研究者データベース

足立 智(アダチ サトル)
工学研究院 応用物理学部門 光波動量子物理工学分野
教授

基本情報

所属

  • 工学研究院 応用物理学部門 光波動量子物理工学分野

職名

  • 教授

学位

  • 工学博士(大阪大学)
  • 工学修士(大阪大学)

J-Global ID

研究キーワード

  • スピントロニクス   量子エレクトロニクス   レーザー分光学   固体光物性   

研究分野

  • 自然科学一般 / 半導体、光物性、原子物理
  • ナノテク・材料 / ナノ構造物理
  • ナノテク・材料 / 応用物性

職歴

  • 2000年 - 2010年 北海道大学 大学院工学研究科 准教授
  • 2010年 - 北海道大学 大学院工学研究院 教授
  • 2010年 - Professor,Graduate School of Enginerring, Hokkaido University
  • 1991年 - 2000年 姫路工業大学 理学部 助手
  • 1991年 - 2000年 Research Associate,School of Science, Himeji Institute of Technology

学歴

  •         - 1991年   大阪大学   工学研究科   電気工学専攻
  •         - 1991年   大阪大学
  •         - 1988年   大阪大学   工学研究科   電気工学専攻
  •         - 1988年   大阪大学
  •         - 1986年   大阪大学   工学部   電気工学科
  •         - 1986年   大阪大学

所属学協会

  • 応用物理学会   The Japan Society of Applied Physics   Laser Society of Japan   The Physical Society of Japan   

研究活動情報

論文

  • Shoichiro Yasui, Masaya Hiraishi, Atsushi Ishizawa, Hiroo Omi, Tomohiro Inaba, Xuejun Xu, Reina Kaji, Satoru Adachi, Takehiko Tawara
    Optics Continuum 1 9 1896 - 1908 2022年08月10日 [査読有り]
  • S. Yasui, M. Hiraishi, A. Ishizawa, H. Omi, R. Kaji, S. Adachi, T. Tawara
    Optics Express 29 17 27137 - 27148 2021年08月16日 [査読有り]
  • S. Yamamoto, R. Kaji, H. Sasakura, S. Adachi
    Japanese Journal of Applied Physics 60 SB SBBH07/1 - SBBH07/4 2021年05月01日 [査読有り]
  • S. Yamamoto, R. Kaji, H. Sasakura, S. Adachi
    Physical Review B 101 24 245424/1 - 245424/8 2020年06月17日 [査読有り]
  • Sota Yamamoto, Takuya Arakawa, Ryosuke Matsusaki, Reina Kaji, Satoru Adachi
    physica status solidi (b) 257 2 1900381/1 - 1900381/5 2020年02月 [査読有り]
  • Masaya Hiraishi, Mark IJspeert, Takehiko Tawara, Satoru Adachi, Reina Kaji, Hiroo Omi, Hideki Gotoh
    Optics Letters 44 20 4933 - 4936 2019年10月15日 [査読有り]
  • S. Yamamoto, R. Matsusaki, R. Kaji, S. Adachi
    Journal of Physics: Conference Series 1220 012047/1 - 012047/4 2019年05月 [査読有り]
  • Reina Kaji, Sota Yamamoto, Ryosuke Matsusaki, Satoru Adachi
    Japanese Journal of Applied Physics 58 SB SBBH10/1 - SBBH10/6 2019年04月01日 [査読有り]
  • Reina Kaji, Ryosuke Matsusaki, Sota Yamamoto, Satoru Adachi
    Japanese Journal of Applied Physics 58 SB SBBH05/1 - SBBH05/5 2019年04月01日 [査読有り]
  • Ryosuke Matsusaki, Reina Kaji, Sota Yamamoto, Hirotaka Sasakura, Satoru Adachi
    Applied Physics Express 11 8 085201/1 - 085201/5 2018年08月01日 [査読有り]
  • Satoru Adachi, Yoshihiro Kawakami, Reina Kaji, Takehiko Tawara, Hiroo Omi
    Applied Sciences 8 6 874/1 - 874/13 2018年05月25日 [査読有り]
  • S. Yamamoto, R. Matsusaki, R. Kaji, S. Adachi
    Physical Review B 97 7 075309/1 - 075309/8 2018年02月26日 [査読有り]
  • Tawara Takehiko, Mariani Giacomo, Shimizu Kaoru, Omi Hiroo, Adachi Satoru, Gotoh Hideki
    Appl. Phys. Express 10 4 042801/1 - 042801/4 Institute of Physics 2017年04月01日 [査読有り]
     
    We investigated spectral-hole narrowing in optical transitions between hyperfine sublevels in isotopically purified erbium ions (167Er3+). The homogeneous broadening Γhof the optical transition was measured in purified and non-purified Er3+-doped crystals via spectral-hole burning. The measured Γhin the purified 167Er3+exhibited a significant reduction of the hole width because the fluctuation of the local magnetic field induced by the electron spins of the surrounding Er3+ions was eliminated. Because the narrowing of the Γhis equivalent to the prolongation of the coherence time, the isotopic purification is effective for the coherent manipulation of quantum states.
  • Takehiko Tawara, Yoshihiro Kawakami, Hiroo Omi, Reina Kaji, Satoru Adachi, Hideki Gotoh
    OPTICAL MATERIALS EXPRESS 7 3 1097 - 1104 2017年03月 [査読有り][通常論文]
     
    We have optically investigated the characteristics of concentration quenching in epitaxial (ErxSc1-x)(2)O-3 layers at the liquid helium temperature as a function of the Er composition (x = 1.000-0.012). Concentration quenching with increasing Er composition was observed at the lowest optical transition energy, although emission lifetimes of 2 ms were maintained from x = 0.012 to 0.270. An analysis of the excitation power dependence of the emission intensity at the lowest and up-converted transition energies revealed that the concentration quenching in high-quality epitaxial (ErxSc1-x)(2)O-3 films mainly originates from the population escaping to the up-conversion states with a high transfer rate, not the population transfer among Er3+ sites to non-radiative centers. (C) 2017 Optical Society of America
  • R. Kaji, T. Tominaga, Y.-N. Wu, M.-F. Wu, S.-J. Cheng, S. Adachi
    physica status solidi (b) 254 2 1600486 - 1600486 2017年02月 [査読有り]
  • L.-P. Yan, T. Takamure, R. Kaji, G. Karczewski, S. Takeyama, S. Adachi
    physica status solidi (b) 254 2 1600449/1 - 1600449/6 2017年02月 [査読有り]
  • Takehiko Tawara, Giacomo Mariani, Kaoru Shimizu, Hiroo Omi, Satoru Adachi, Hideki Gotoh
    Conference on Lasers and Electro-Optics (CLEO:2017) 2017年 [査読有り][通常論文]
     
    We report effect of isotope separation on the homogeneous linewidth in Er3+-doped Y2SiO5 measured by using spectral hole burning. Isotope Er-167(3+) provides a drastic reduction of the spectral hole width by strongly suppressing instantaneous spectral diffusion.
  • R. Kaji, T. Tominaga, Y. -N. Wu, M. -F. Wu, S. -J. Cheng, S. Adachi
    The 43rd International Symposium on Compound Semiconductors (ISCS) 2016年 [査読有り][通常論文]
     
    We investigated the electron and hole g-factors in individual InAs/GaAs quantum rings (QRs). From the magneto-photoluminescence measurements under a transverse magnetic field, we evaluated the in-plane g-factors of electron and hole spins by rotating the sample systematically around the crystal growth axis. The experimental results indicate that the in-plane and the out-of-plane anisotropies in hole g-factor are larger than those of electron g-factor, and the value of the hole in-plane g-factor varies largely from QR to QR while the electron g-factor is almost a constant value. From the model calculation considering the effects of shape anisotropies and uniaxial stress, we examined the correlation between the in-plane g-factors and the degree of valence band mixing. Further, the experimentally obtained trend in g-factors was in agreement qualitatively with theoretical consideration.
  • Takehiko Tawara, Hiroo Omi, Thomas McManus, Aleix Llenas, Eiichi Kuramochi, Satoru Adachi, Hideki Gotoh
    The 43rd International Symposium on Compound Semiconductors (ISCS) 2016年 [査読有り][通常論文]
  • L. -P. Yan, R. Kaji, S. Adachi
    The 43rd International Symposium on Compound Semiconductors (ISCS) 2016年 [査読有り][通常論文]
     
    We have studied the spin dynamics of the resident electron spin polarization (RESP) based on the initial phase shift of the Larmor precessions in a CdTe single quantum well by using a time-resolved Kerr rotation technique. The generation dynamics of RESP involve the formation and transformation of the associated optically excited states and are complicated particularly in the early time region. A careful analysis of the phase shift gives a deep understanding of the generation processes. In the experiments in the excitation energy range between the negative trion and neutral exciton resonances, the anomalous negative phase shift was observed, and the mechanism associated especially with a quick hole spin-flip and transformation to trions from excitons are discussed through the dependences on excitation energy, excitation power, and magnetic field strength.
  • S Adachi, Y Kawakami, R Kaji, T Tawara, H Omi
    Journal of Physics: Conference Series 647 012031 - 012031 2015年10月13日 [査読有り]
  • Yan Li-Ping, Kurosawa Masahiro, Hsu Wei-Ting, Chang Wen-Hao, Adachi Satoru
    Jpn. J. Appl. Phys. 54 3 033003 - 033003 Institute of Physics 2015年03月01日 [査読有り]
     
    Longitudinal and in-plane electron g-factors, and a nuclear spin polarization (NSP) have been evaluated precisely in a CdTe/Cd0.85Mg0.15Te single quantum well by using the time-resolved Kerr rotation and double lock-in detection techniques. Resident electron spin polarization (RESP) was formed via the negative trion formation and recombination, and RESP gave rise to NSP in an oblique magnetic field configuration. We observed the effective nuclear field of a few mT which was weak compared with that in III–V semiconductor nanostructures as expected, but the nuclear field can be converted to the maximal NSP of 12% in Faraday geometry.
  • R. Kaji, T. Tominaga, Y. -N. Wu, S. -J. Cheng, S. Adachi
    19TH INTERNATIONAL CONFERENCE ON ELECTRON DYNAMICS IN SEMICONDUCTORS, OPTOELECTRONICS AND NANOSTRUCTURES (EDISON' 19) 647 012011/1 - 4 2015年 [査読有り][通常論文]
     
    The electron and hole in-plane g-factors were studied in individual InAs/GaAs quantum rings (QRs). From the magneto-photoluminescence measurements under a transverse magnetic field, we evaluated the in-plane g-factors of electron and hole spins by rotating the sample systematically along the crystal growth axis. The experimental results indicate that the in-plane and the out-of-plane anisotropies in hole g-factor are larger than those of electron g-factor, and the value of the hole in-plane g-factor varies largely from QR to QR while the electron g-factor is almost a constant value. From the model calculation considering the effects of shape anisotropies and uniaxial stress, we examined the correlation between the in-plane g-factors and the degree of valence band mixing. Further, the experimentally obtained trend in g-factors was in agreement qualitatively with theoretical consideration.
  • T. Tawara, T. McManus, Y. Kawakami, H. Omi, A. Najar, R. Kaji, S. Adachi, H. Gotoh
    2015 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) 2015年 [査読有り][通常論文]
     
    Visible up-conversion luminescence induced by 1535-nm excitation in (ErSc)(2)O-3 epitaxial layers are observed. We investigate fast up-conversion rate and propose its suppression structure by photonic band-gap for realizing higher optical gain devices on Si wafers.
  • Yan L. -P., Kurosawa M., Kaji R., Karczewski G., Takeyama S., Adachi S.
    Physical Review B 90 20 American Physical Society 2014年11月19日 [査読有り]
     
    Initial phase shift in a precessional motion of resident electron-spin polarization is studied in a CdTe/Cd0.85Mg0.15Te single quantum well using a time-resolved Kerr rotation technique. The generation dynamics of resident electron-spin polarization involve the formation and transformation of the associated optically excited states and are complicated particularly in the early time region. A careful analysis of the phase shift gives a deep understanding of the generation processes. In the experiments, the negative phase shift of the resident electron-spin polarization is observed, and the mechanism associated especially with a quick hole spin flip in negative trions is studied through the dependences on excitation power and magnetic field strength.
  • Kaji Reina, Hozumi Takahito, Hachiyama Yuta, Tomii Takuma, Sasakura Hirotaka, Jo Masafumi, Adachi Satoru
    Appl. Phys. Express 7 6 065002 - 065002 Institute of Physics 2014年06月01日 [査読有り]
  • Li Ping Yan, Reina Kaji, Satoru Adachi
    Advanced Materials Research 936 534 - 539 2014年06月 [査読有り]
     
    Effective magnetic field of nuclear spin polarization (NSP) under circularly polarized pumps excitation and the dephasing time of resident electron spin polarization under pump and control excitation has been detected in a single CdTe quantum well (QW) by a time-resolved Kerr rotation (TRKR) technique. We deduced that the experimental method is verified with the effect, to a certain extent, through confirming the external magnetic field results. In addition, the nuclear field is revealed to be increased with the increasing electron spin component due to the enhanced electron-nuclear hyperfine interaction. Significant nuclear field is observed as 1.85 mT with the applied magnetic field tilted by about 15 degree. What is more, we found the spin dephasing time (SDT) has little relation with the created NSP field, but it decreases largely with the increasing spin polarization magnitude under pump excitation and the spin vector dispersions induced by control pulses.
  • T. Tawara, H. Omi, A. Najar, R. Kaji, S. Adachi, H. Gotoh
    2014 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO) 2014年 [査読有り][通常論文]
     
    Toward quantum information applications, we control the interactions between Er ions by alloying epitaxial Er2O3 with scandium and suppress energy transfer and inhomogeneous broadening of Stark levels in the intra-4f band of Er ions.
  • Toda Yasunori, Shigematsu Kyohhei, Hasegawa Akira, Adachi Satoru
    Jpn J Appl Phys 52 8S 08JL03 - 08JL03 The Japan Society of Applied Physics 2013年08月01日 [査読有り]
     
    We report on the four-wave mixing (FWM) spectroscopy of excitons in tensile-strained GaN films. Three excitonic resonances (A-, B-, and C-excitons) were clearly observed with energy separations of \Delta_{\text{AB } }\sim 4.7 meV and \Delta_{\text{BC } }\sim 14.5 meV. Owing to tensile strain, these values are much smaller than those of free-standing GaN, allowing the simultaneous excitations of A--B and B--C excitons pairs. The time evolutions of the FWM in different polarization configurations resolved the differences in the simultaneous excitonic transitions; the excitation of A--B excitons showed an oscillation with a critical \pi-phase shift in the orthogonal polarization configuration as expected in the quantum beat, and the oscillation of B--C excitons pair is independent of the polarization configuration, indicating polarization interference. The polarization-dependent FWM spectra of A--B excitons revealed peaks associated with biexciton transitions with binding energies of E_{\text{AA } } = 4.6 meV, E_{\text{AB } } = 2.1 meV, and E_{\text{BB } } = 1.7 meV.
  • T. Tawara, H. Omi, T. Hozumi, R. Kaji, S. Adachi, H. Gotoh, T. Sogawa
    Applied Physics Letters 102 24 241918 - 241918 2013年06月17日 [査読有り]
  • R. Kaji, S. Ohno, T. Hozumi, S. Adachi
    JOURNAL OF APPLIED PHYSICS 113 20 203511/1 - 6 2013年05月 [査読有り][通常論文]
     
    The effects of valence band mixing on the hole spin coherence in self-assembled InAlAs quantum dots are investigated. The valence band mixing induces not only optical anisotropy in the quantum dot emissions but also heavy hole spin dephasing via the hyperfine interaction with the lattice nuclei. We evaluated the degree of valence band mixing for a number of In0.75Al0.25As/Al0.3Ga0.7As quantum dots from experiments. The magnitude of valence band mixing does not show a clear dependence on the photoluminescence energy, and it is less than 0.25 in our sample. Although the direct measurement with experimental methods has not been carried out at this stage, the effect of valence band mixing on the hole spin coherence is discussed in detail by the calculations. (C) 2013 AIP Publishing LLC.
  • Xiangmeng Lu, Masataka Koyama, Yoshiharu Izumi, Yoshiaki Nakata, Satoru Adachi, Shunichi Muto
    JAPANESE JOURNAL OF APPLIED PHYSICS 52 2 025602/1 - 4 2013年02月 [査読有り][通常論文]
     
    We studied the size distribution and scaling behavior of self-assembled InAlAs/AlGaAs quantum dots (QDs) grown on GaAs in the Stranski-Krastanow (SK) mode by molecular beam epitaxy (MBE) at 480 and 510 degrees C as a function of InAlAs coverage. A scaling function of the volume was found for the first time in ternary alloy QDs. The function was similar to that of InAs/GaAs QDs, which agreed with the scaling function for a two-dimensional submonolayer homoepitaxy simulation with a critical island size of i = 1. However, a characteristic of i = 0 was also found as a tail in a large volume. (C) 2013 The Japan Society of Applied Physics
  • T. Tawara, T. Hozumi, H. Omi, R. Kaji, S. Adachi, H. Gotoh, T. Sogawa
    2013 IEEE Photonics Conference, IPC 2013 149 - 150 2013年 [査読有り][通常論文]
     
    Time constants of a resonant energy transfer between Er ions in epitaxial Er2O3 grown on Si(111) are investigated for the coherent manipulation of populations and experimentally estimated to be several microseconds by resonant excitation photoluminescence. © 2013 IEEE.
  • A. Takagi, A. Nakamura, A. Yoshikaie, S. Yoshioka, S. Adachi, S. F. Chichibu, T. Sota
    J. Phys.: Condens. Matter 24 41 415801/1 - 8 2012年10月 [査読有り][通常論文]
     
    Theoretical and experimental studies were carried out on exciton-polaritons excited in ZnO. Polaritons in which both Gamma(1) and Gamma(5) excitons couple to electromagnetic waves simultaneously are shown to exist, and their signatures are observed in polarized reflectance spectra measured under k perpendicular to a and E parallel to c configurations for an m-plane sample. Theoretical calculations reveal that the mixed-mode polaritons consist of one Gamma(1) transverse mode and two Gamma(5) longitudinal modes. It is also shown that the signatures are sensitive to the valence band ordering.
  • K. Hazu, S. F. Chichibu, S. Adachi, T. Sota
    JOURNAL OF APPLIED PHYSICS 111 9 093522/1 - 6 2012年05月 [査読有り][通常論文]
     
    Spectroscopic and temporal four-wave-mixing (FWM) measurements are carried out on a strain-free bulk ZnO single crystal, in order to clarify the valence-band-ordering. Under the collinearly polarized lights with the electric-field component parallel to the c-axis, which can excite dipole-allowed Gamma(1)-excitons, the FWM signal appears only in the energies corresponding to the B-exciton. Under the cross-linear polarization configuration exciting both Gamma(5)- and Gamma(1)-excitons, the FWM signal arising from the two-photon-coherence is absent in the energies corresponding to A-exciton. Both the results indicate that Gamma(1)-exciton state belongs exclusively to B-exciton, meaning that the valence-band ordering is Gamma(9) - Gamma(7) - Gamma(7) in order of decreasing electron energy for the present strain-free ZnO single crystal. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4711103]
  • S. Adachi, R. Kaji, S. Furukawa, Y. Yokoyama, S. Muto
    JOURNAL OF APPLIED PHYSICS 111 10 103531/1 - 6 2012年05月 [査読有り][通常論文]
     
    Nuclear spin diffusion in single self-assembled InAlAs quantum dots was studied by using erase-pump-probe technique. As a measure of nuclear spin polarization, transients of the Overhauser shift (OHS) of positive trion were probed in the respective pulse region. The achieved stable OHS was relaxed with a long depolarization time as long as a few tens of seconds and a diffusion constant of similar to 5 x 10(-15) cm(2)/s was estimated. The slow transfer of the spin energy is considered to be due to the dipole-dipole interaction of the nuclei. In addition, through the magnetic field dependence of OHS, the stability of the nuclear spin polarization was briefly discussed, and the saturated maximum values of OHS were investigated experimentally. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4721902]
  • R. Kaji, S. Adachi, H. Sasakura, S. Muto
    PHYSICAL REVIEW B 85 15 155315/1 - 6 2012年04月 [査読有り][通常論文]
     
    The spin interaction between an electron and nuclei was investigated optically in a single self-assembled InAlAs quantum dot (QD). In spin dynamics at the initial stage, the fluctuation of nuclear field and the resulting electron spin relaxation time play a crucial role. We examined a positively charged exciton in a QD to evaluate the key physical quantities directly via the temporal evolution measurements of the Overhauser shift and the degree of circular polarization. In addition, the validity of our used spin dynamics model was discussed in the context of the experimentally obtained key parameters.
  • X. M. Lu, Y. Izumi, M. Koyama, Y. Nakata, S. Adachi, S. Muto
    JOURNAL OF CRYSTAL GROWTH 322 1 6 - 9 2011年05月 [査読有り][通常論文]
     
    The effects of growth conditions on the size and density of self-assembled InAlAs/AlGaAs quantum dots (QDs) grown on GaAs by molecular beam epitaxy (MBE) were studied with an emphasis on their use for single QD spectroscopy. The effects of substrate temperature and growth rate on the density and size were found to be quite similar to those of InAs QDs on GaAs. The effect of coverage, however, was different. Although the density was relatively high as compared to that of InAs QDs, it was reduced to 1 x 10(10) cm(-2) under an optimized condition. This density is compatible with single QD spectroscopy with the help of a certain nanofabrication technique for areal restriction. (C) 2011 Elsevier B.V. All rights reserved.
  • Sou Ryuzaki, Toshihiro Kai, Yasunori Toda, Satoru Adachi, Jun Onoe
    JOURNAL OF PHYSICS D-APPLIED PHYSICS 44 14 145103/1-145103/1 - 4 2011年04月 [査読有り][通常論文]
     
    We have examined the structural effects of zinc-octaethylporphyrin [Zn(OEP)] films used as a donor on the external quantum efficiency (EQE) of organic heterojunction photovoltaic (OPV) cells [ITO/Zn(OEP)/C-60/Al], and investigated what exactly causes the improvement of EQE. When the structure of the Zn(OEP) films changed from amorphous to crystalline, the maximum EQE increased from 36% to 42%, which is greater than that of around 35% for previously reported OPV cells using buffer materials (Peumans and Forrest 2001 Appl. Phys. Lett. 79 126). The crystallization of Zn(OEP) films is found to increase the number of inter-molecular charge-transfer (IMCT) excitons and to enlarge the mobility of carriers and IMCT excitons, thus significantly improving the EQE of the photoabsorption band under illumination due to the IMCT excitons.
  • S. Ohno, S. Adachi, R. Kaji, S. Muto, H. Sasakura
    APPLIED PHYSICS LETTERS 98 16 161912/1-161912/1 - 3 2011年04月 [査読有り][通常論文]
     
    We have investigated the optical anisotropy in individual self-assembled quantum dots. The linear polarization analysis of the positive trion photoluminescence reveals the effect of the strain-induced valence band mixing since the positive trion has the spin-paired holes and therefore exchange interaction has no influence. Meanwhile, the neutral exciton indicates the complex polarization states due to both the in-plain asymmetries of the dot shape and the strain distributions. The experimental and theoretical polarization analysis has been performed for tens of InAlAs quantum dots and the correlation between the important parameters was investigated. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3583453]
  • R. Kaji, S. Adachi, S. Muto
    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 1 8 1 30 - 33 2011年 [査読有り][通常論文]
     
    Polarization properties of the exciton emissions from single InAlAs/AlGaAs quantum dots were investigated by using Hanle-like measurement. The in-plane exchange field drives the exciton spin precession even under zero external magnetic field and the polarization of emissions can be converted from circular to linear and vice versa. Longitudinal applied magnetic field increases the conversion ratio up to the theoretical limit similar to 50%, where the field strength is comparable to the exchange field. Finally, the effect of valence band mixing on the polarization conversion was discussed. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • K. Tomoda, S. Adachi, S. Muto, S. Shimomura
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 42 10 2714 - 2717 2010年09月 [査読有り][通常論文]
     
    Exciton spin and phase relaxations at low temperatures in GaAs/AlGaAs single quantum wells were investigated by using transient grating technique. The technique allows us to obtain the exciton lifetime, spin relaxation, and phase relaxation in the same setup. In combination with a series of single quantum wells grown on the same substrate, the well width dependence of exciton spin relaxation was studied. The obtained spin relaxation results were analyzed with their phase relaxation times in a framework of MAS mechanism, and were in good agreement with the calculated results. Especially, the motional narrowing character of the exciton spin relaxation was well demonstrated. (C) 2009 Elsevier B.V. All rights reserved.
  • R. Kaji, T. Shindo, S. Adachi, S. Muto
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 42 10 2501 - 2504 2010年09月 [査読有り][通常論文]
     
    We demonstrated the circular to linear polarization conversion in single InAlAs/AlGaAs QDs. Since the anisotropic exchange interaction acts on the photo-created exciton spin as an in-plane effective magnetic field, the polarization of emissions can be converted from circular to linear and vice versa even under a zero external magnetic field. By using the quasi-resonant excitation, high conversion ratio up to similar to 50% was obtained under nonzero longitudinal magnetic field. Additionally, exciton spin relaxation time and built-in linear dichroism were estimated by exciton spin dynamics in the 3D pseudospin precession model. (C) 2010 Elsevier B.V. All rights reserved.
  • R. Kaji, S. Adachi, T. Shindo, S. Muto
    PHYSICAL REVIEW B 80 23 235334/1 - 6 2009年12月 [査読有り][通常論文]
     
    The polarization conversion from optical orientation to alignment in single InAlAs/AlGaAs quantum dots (QDs) was studied in detail under zero and nonzero magnetic fields. Under the influence of the effective magnetic field, bright exciton doublets precess in pseudospin space, where the torque vector is composed of the external magnetic field and the anisotropic exchange field. For a number of QDs, we measured the angle difference of the polarization axes obtained with circularly polarized excitations, which is an indicator of the conversion efficiency under a zero magnetic field. By applying a longitudinal magnetic field, a high conversion efficiency of similar to 50% was achieved. Additionally, the exciton spin-relaxation time and the magnitude of built-in linear dichroism were estimated from the exciton spin dynamics using the three-dimensional pseudospin precession model, and a long spin-relaxation time exceeding the recombination lifetime was obtained. Finally, we discussed the influence of a nuclear magnetic field on the polarization conversion.
  • Y. Ueno, Y. Toda, S. Adachi, R. Morita, T. Tawara
    OPTICS EXPRESS 17 22 20567 - 20574 2009年10月 [査読有り][通常論文]
     
    We demonstrate the coherent transfer of optical orbital angular momentum (OAM) to the center of mass momentum of excitons in semiconductor GaN using a four-wave mixing (FWM) process. When we apply the optical vortex (OV) as an excitation pulse, the diffracted FWM signal exhibits phase singularities that satisfy the OAM conservation law, which remain clear within the exciton dephasing time (similar to 1ps). We also demonstrate the arbitrary control of the topological charge in the output signal by changing the OAM of the input pulse. The results provide a way of controlling the optical OAM through carriers in solids. Moreover, the time evolution of the FWM with OAM leads to the study of the closed-loop carrier coherence in materials. (C) 2009 Optical Society of America
  • Tetsuro Ishiguro, Yasunori Toda, Satoru Adachi
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 10 104718/1-104718/4  2009年10月 [査読有り][通常論文]
     
    We study the influence of the anisotropic exchange interaction (AEI) on exciton coherence by using four-wave-mixing spectroscopy. The exciton fine structure (FS) of uniaxially-strained GaN exhibits linearly-polarized FS-splitting at low temperatures, which enables us to resolve the difference between the coherent dynamics of the FS; the FWM transient in each FS exhibits extended/contracted dephasing compared with that obtained in uniformly-strained GaN. The origin of this asymmetry is associated with the anisotropic pseudospin induced by AEI.
  • H. Kumano, S. Ekuni, H. Kobayashi, H. Sasakura, I. Suemune, S. Adachi, S. Muto
    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 246 4 775 - 778 2009年04月 [査読有り][通常論文]
     
    High degree of preservation of spin states mediated by optical phonons is demonstrated with a positive trion state in a single quantum dot. At the optical phonon resonance suppression of spin relaxation is clearly identified as a dip structures in photoluminescence excitation spectra under cross-circularly polarize detection with respect to a pumping. As a result, distinguishably high degree of circular polarization up to similar to 0.85 is achieved in the absence of external magnetic field, which is no the case for neutral excitons with finite fine structure splitting. The absence of continuum states plays a crucial role for this observation. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • H. Sasakura, S. Adachi, R. Kaji, K. Yamada, S. Muto
    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 246 4 784 - 787 2009年04月 [査読有り][通常論文]
     
    We investigated an optically created nuclear field in a single InAlAs quantum dot and demonstrated that the zero effective electron g-factor could be achieved by the cancellation of the external magnetic field by the nuclear field at one edge of the nuclear polarization bistability. In addition, we discussed more practical way to realize the zero g-factor using the unique maximum value of the nuclear field, which keeps steady value against the fluctuation of excitation power. The cancellation for the electron Zeeman splitting provides the accurate hole g-factor. Since exciton g-factor is obtained by the Zeeman splitting without the nuclear field due to the linearly polarized excitation, we can evaluate the magnitudes and the signs of electron and hole g-factors in the growth direction of the single quantum dot. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • T. Ishiguro, Y. Toda, S. Adachi, K. Tadatomo, K. Hoshino
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 6, NO 1 6 1 42 - + 2009年 [査読有り][通常論文]
     
    Dephasing dynamics of exciton fine structure (EFS) caused by long and short range exchange interactions in GaN was investigated by using a four-wave-mixing (FWM) spectroscopy. The type of exchange interactions was selected by samples (uniaxially strained c-plane GaN films and a thick bulk GaN) and their geometries in optical excitation. Since each component of EFS is highly polarized, the polarization-dependent FWM spectra successfully resolve the dephasing dynamics in the individual EFS resonances. The results show a difference in dephasing time, suggesting a contribution of anisotropic exchange interaction (AEI). (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • H. Sasakura, S. Adachi, R. Kaji, S. Muto
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 6, NO 4 6 4 837 - + 2009年 [査読有り][通常論文]
     
    We demonstrated the creation of nanoscale magnetic field into the two isolated semiconductor quantum dots in spatially-confined mesa structure of similar to 150 nm diameter using an optical pumping of the nuclear spins. The amplitude of nuclear field between two isolated quantum dots under same pumping condition were clearly difference, suggesting that the nanoscale-locality of the nuclear field was found to be around 100 nm. This method is based on the sensitivity of the critical magnitudes of the external magnetic field to the quantum dot properties in the bistable behavior of nuclear spin polarization. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • Y. Toda, K. Yamaguchi, T. Ishiguro, K. Hoshino, K. Tadatomo, S. Adachi
    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 6, SUPPL 2 6 S684 - S686 2009年 [査読有り][通常論文]
     
    Spatial imaging of spectrally-resolved four-wave mixing (SR FWM) was performed on a GaN film grown on c-sapphire substrate. The image obtained from the exciton resonances at zero time delay clearly showed some highly localized reductions in their intensities whose spatial profiles can be mapped out with a spatial resolution of similar to 20 m. The image obtained from the evaluation of the quantum beats indicates these reductions correspond to the phase changes between two exciton transitions, reflecting the spatial properties of exciton-exciton interactions. The line-localization suggests a contribution of line-defect to the anomalous interactions. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • T. Ishiguro, Y. Toda, S. Adachi, S. F. Chichibu
    PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 6, SUPPL 2 6 S719 - S722 2009年 [査読有り][通常論文]
     
    We report on the dephasing dynamics of exciton fine structure (EFS) in a free standing GaN. The EFS was observed and studied by utilizing a four-wave-mixing (FWM) spectroscopy. In the cleavage plane of wurtzite GaN, we can excite the B-exciton fine structure, whose z-polarized state is energetically well separated from the other in-plane polarized exciton states. Due to the large spin exchange interaction in GaN, an energy shift of in-plane polarized fine structure was also observed. Since the each component of EFS is highly polarized, the polarization-dependent FWM successfully resolves their dephasing dynamics. The results show a significant difference in the dephasing time between EFS, suggesting that anisotropic exchange interaction is effective as reported in our previous work using a GaN film on alpha-plane sapphire. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • R. Kaji, K. Yamada, H. Sasakura, S. Adachi
    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 245 12 2662 - 2666 2008年12月 [査読有り][通常論文]
     
    Precise optical evaluation of electron and hole g-factors in single InAlAs quantum dot was performed by using the optical pumping of nuclear magnetic field and its bistable behavior. The measurement is based on the fact that the induced nuclear field is effective only on electrons and can compensate the external magnetic field. The experimental results indicate that the effective electron g-factor can change in large magnitude including the sign in a controllable manner. Therefore, the method will be useful for the spin manipulation experiments such as photon-spin qubit conversion. In addition, the in-plane electron and hole g-factors were measured in Voigt geometry. This is the first report of individual g-factors of electron and hole in single InAlAs/AlGaAs quantum dots, which have been reported so far by only a few studies about the exciton g-factor. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • H. Kumano, H. Kobayashi, S. Ekuni, Y. Hayashi, M. Jo, H. Sasakura, S. Adachi, S. Muto, I. Suemune
    PHYSICAL REVIEW B 78 8 081306(R)/1 - 4 2008年08月 [査読有り][通常論文]
     
    High degree of excitonic spin-state preservation during energy relaxation is demonstrated in a single quantum dot. Optical-phonon resonances and corresponding suppression of spin relaxation are clearly identified as dip structures in photoluminescence excitation spectra probed by the positive trion emission. Consequently, under the longitudinal optical-phonon resonant excitation, a distinguishably high degree of circular polarization up to similar to 0.85 is achieved. Extended spin-relaxation time in the positive trion ground state compared to that in neutral exciton ground state is also revealed.
  • H. Sasakura, S. Adachi, S. Muto, S. Hirose, H. Z. Song, M. Takatsu
    JOURNAL OF APPLIED PHYSICS 103 10 103530/1 - 5 2008年05月 [査読有り][通常論文]
     
    The oscillations of excitonic and nuclear spin polarizations in an optically pumped single self-assembled In0.8Al0.2As/Al0.35Ga0.65As quantum dot (QD) were clearly observed under the excitation of a wetting layer edge at B=5 T. This indicates that an exciton pair with opposite spins is alternatively created via the half-localized state only by changing the delay time between cross-linearly polarized pulse pair. Furthermore, periodic modulation of Zeeman energy synchronizes the degree of circular polarization of photoluminescence from a single QD, indicating that the Overhauser field follows the optically created electron spin polarization in half-localized states of a QD, and the half-localized state in a QD consists of a confined electron in a discrete state and hole in the continuum state. (C) 2008 American Institute of Physics.
  • Y. Toda, T. Ishiguro, S. Adachi, K. Hoshino, K. Tadatomo
    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 245 5 878 - 880 2008年05月 [査読有り][通常論文]
     
    We have previously demonstrated that a spectrally-resolved four-wave mixing highlights the anisotropically polarized excitons in the uniaxially strained GaN films [1], where the enhancement of sensitivity for an uniaxial strain, was achieved by nonlinear response of the exciton polarization. In this work, we have applied this technique to the GaN films on various substrates including isotropic ones, and have examined the sensitivity of the technique. The results show distinct polarizations and energy variations originating from the uniaxial strain, the magnitude of which depends on the sample and its position: The minimum changes of the polarized FWM intensity and exchange energy splittings correspond to a uniaxial strain of 5.0 x 10(-5), which currently gives a lower resolution limit of this technique. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • H. Kumano, H. Kobayashi, Y. Hayashi, M. Jo, I. Suemune, H. Sasakura, S. Adachi, S. Muto
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 40 6 1824 - 1827 2008年04月 [査読有り][通常論文]
     
    Single photon emission with high degree of circular polarization (DCP) from a positively charged exciton (trion) state in a single quantum dot (QD) is demonstrated under zero magnetic field. Obtained high DCP as large as 0.6 is a clear manifestation of highly effective mutual polarization conversion between single photon and single electron spin. This finding also reveals that the spin relaxation is strongly suppressed during capture and thermalization processes and also in trion ground states in a QD. Moreover, exciton charging state control is shown to be possible by modifying the electron capture probability through the excitation energy tuning, which leads to an exclusive formation of the positive trion in a QD. (c) 2007 Published by Elsevier B.V.
  • R. Kaji, S. Adachi, H. Sasakura, S. Muto
    PHYSICAL REVIEW B 77 11 115345/1 - 5 2008年03月 [査読有り][通常論文]
     
    Optically pumped nuclear spin polarization in single InAlAs quantum dots was investigated in detail with regards to the dependences on the excitation power and electron spin polarization. By increasing (or decreasing) the excitation power at a particular excitation polarization, an abrupt rise (or drop) and a clear hysteretic behavior were observed in the Overhauser shift of the photoluminescence under an external magnetic field of 5 T. Those features appear equivalently for the exciton and exciton complexes of the same quantum dot since the created nuclear field is equally effective. However, the degree of circular polarization shows different behaviors between a positively charged exciton and a neutral exciton or biexciton; further, only the positively charged exciton exhibits the precisely synchronized change and hysteretic behavior. It is suggested that the electron spin distribution is affected by the flip-flop of electron-nuclear spins. Further, the hysteresis is observed as a function of the degree of circular polarization of the excitation light, and its dependence on the excitation power is studied. The saturation of the Overhauser shift indicates the almost complete cancellation of the external magnetic field by the nuclear field.
  • H. Kobayashi, H. Kumano, M. Endo, M. Jo, I. Suemune, H. Sasakura, S. Adachi, S. Muto
    MICROELECTRONICS JOURNAL 39 3-4 327 - 330 2008年03月 [査読有り][通常論文]
     
    Origin of sharp photoluminescence lines observed from an InAlAs quantum dot was identified with the measurements of excitation-power dependences and polarization correlations, together with photon correlation measurements. Single photon emission with high degree of circular polarization (DCP) up to 60% was observed from a positively charged exciton (trion) state in the single quantum dot under non-resonant excitation at zero magnetic field. (C) 2007 Elsevier Ltd. All rights reserved.
  • R. Kaji, H. Sasakura, S. Adachi, S. Muto
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 1 5 1 298 - + 2008年 [査読有り][通常論文]
     
    In a single self-assembled InAlAs quantum dot, we report the nonlinearity of nuclear spin polarization by optical pumping. Increasing (or decreasing) the excitation power at a particular excitation polarization, nuclear spin polarization shows the abrupt jump (or drop) and a clear hysteresis loop. In addition, the degree of circular polarization of positively charged exciton also exhibits similar bistable behavior and the hysteretic operation has the precise synchronization with the nuclear spin polarization. It suggests that an electron in the positively charged exciton plays a main role to create the abrupt change of the nuclear spin polarization in the observed quantum dot. This abrupt change reveals the sign and magnitude of the electron g-factors in z-direction and can be explained by using a simple model calculation. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • S. Adachi, H. Sasakura, N. Yatsu, R. Kaji, K. Yamada, S. Muto, H. Kumano, I. Suemune
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 1 5 1 351 - + 2008年 [査読有り][通常論文]
     
    We report the photon-correlation Fourier spectroscopy of exciton and exciton complexes in single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dots. A Michelson interferometer inserted in the photoluminescence path was used to measure the coherent length of the time-averaged emission of neutral exciton, biexciton, and positive trion. As comparing with their coherence time and their excitation energy dependence, the effects of the exchange interaction and the fluctuation of the surrounding excess charge are discussed.
  • T. Ishiguro, Y. Toda, S. Adachi, K. Hoshino, Y. Arakawa
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 5, NO 6 5 6 2114 - + 2008年 [査読無し][通常論文]
     
    Dephasing dynamics of excitons in a GaN film grown on a-plane sapphire were studied by using the spectrally-resolved four-wave-mixing (SR-FWM) spectroscopy. Due to the anisotropic exchange interaction originates from the anisotropic strain field of the substrate, the degenerate exciton states with the total angular moment +/- 1 mix and split into their fine structures. Since each component of the exciton fine structured (EFS) is highly polarized, the polarization-dependent SR-FWM spectra successfully resolve the dephasing dynamics in the individual EFS resonances. The result of each EFS shows a significantly different dephasing time, suggesting that the anisotropic dephasing contribution occurs in each EFS.
  • H. Sasakura, R. Kaji, S. Adachi, S. Muto
    APPLIED PHYSICS LETTERS 92 4 041915/1 - 3 2008年01月 [査読有り][通常論文]
     
    We investigated an optically created nuclear field in a single InAlAs quantum dot and demonstrated that the nuclear field can be used to discriminate whether photoluminescence lines originate from the same dot or a different dot. Since the nonlinear response of the nuclear field is sensitive to the electron g factor and correlation time of a coupled electron-nuclear spin system, the resultant Overhauser shift is their good measure for individual quantum dots. This method provides a simple and convenient alternative to the standard photon cross-correlation method. (c) 2008 American Institute of Physics.
  • T. Ishiguro, Y. Toda, S. Adachi, S. F. Chichibu
    ULTRAFAST PHENOMENA IN SEMICONDUCTORS AND NANOSTRUCTURE MATERIALS XII 6892 689219/1 - 11 2008年 [査読無し][通常論文]
     
    We perform degenerate four-wave-mixing (FWM) studies of GaN excitons especially for an understanding of the strain-fields in the heteroepitaxial films. The shifts of exciton energies and their beating oscillation variations highlight the biaxial strain, allowing for a precise determination of the strain parameters. The uniaxial strain field can be characterized by the polarization dependence of FWM, which shows distinct polarizations and energy variations depending on the sample and its position. The minimum changes of the polarized FWM intensity and exchange energy splittings correspond to a uniaxial strain of 5.0 x 10(-5). which currently gives a lower resolution limit of this technique and is comparable with that of conventional X-ray diffraction. In the time-evolutions, we investigate the strain effects on the phase of the quantum beats (QBs), giving insight into the excitons interactions. By using time-resolved FWM, difference between two-types of exciton transitions is identified. In addition, coherent manipulations of QBs are successfully realized in the FWM with a Michelson interferometer.
  • R. Kaji, S. Adachi, H. Sasakura, S. Muto
    APPLIED PHYSICS LETTERS 91 26 261904/1 - 3 2007年12月 [査読有り][通常論文]
     
    We demonstrated the cancellation of the external magnetic field by the nuclear field at one edge of the nuclear polarization bistability in single InAlAs quantum dots. The cancellation for the electron Zeeman splitting gives the precise value of the hole g factor. In combination with the exciton g factor that is obtained from the Zeeman splitting for linearly polarized excitation, the magnitude and the sign of the electron and hole g factors in the growth direction are evaluated. (c) 2007 American Institute of Physics.
  • S. Adachi, N. Yatsu, R. Kaji, S. Muto
    APPLIED PHYSICS LETTERS 91 16 161910/1 - 3 2007年10月 [査読有り][通常論文]
     
    We report the single-photon Fourier spectroscopy of exciton and exciton complexes in single self-assembled InAlAs/AlGaAs quantum dots. A Michelson interferometer was inserted in the photoluminescence path for measuring the coherence length of the time-averaged emission of neutral excitons and their complexes. The effects of exchange interactions and fluctuations in the surrounding excess charges were estimated by comparing the coherence times and the excitation energies of the excitons and their complexes. (C) 2007 American Institute of Physics.
  • R. Kaji, S. Adachi, H. Sasakura, S. Muto, H. Kumano, I. Suemune
    JOURNAL OF SUPERCONDUCTIVITY AND NOVEL MAGNETISM 20 6 447 - 451 2007年08月 [査読有り][通常論文]
     
    We investigated optical pumping of nuclear spin polarizations in a single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dot. The nuclear spin polarization exhibits the abrupt jump and hysteresis in the excitation power dependence at a particular excitation polarization. Measurement of circular polarization rate of the photoluminescence reveals that the abrupt change of the nuclear spin polarization is created mainly by the spin flip-flop process between nuclei and an electron of a positive charged exciton in this single quantum dot. Model calculation explains well the experimentally observed bistable behavior in InAlAs quantum dot. By using this abrupt change, the sign and magnitude of electron and hole g-factors in z-direction are verified.
  • H. Sasakura, S. Kayamori, S. Adachi, S. Muto
    JOURNAL OF APPLIED PHYSICS 102 1 013515/1 - 4 2007年07月 [査読有り][通常論文]
     
    The control of the emission energy from self-assembled InAs quantum dots has been demonstrated by using indium flush. The low-temperature indium-flush method was found to control the emission energy preserving the high structural uniformity attributed to the slow dot growth. In the standard indium-flush method, where the substrate temperature was raised up from the dot-growth temperature, blueshift larger than the shift by the low-temperature indium flush was observed and was explained reasonably by the enhanced In/Ga-interdiffusion. Also, the effect of AlGaAs capping layer before the indium-flush step was studied. (c) 2007 American Institute of Physics.
  • T. Ishiguro, Y. Toda, S. Adachi, K. Hazu, T. Sota, S. F. Chichibu
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 4 NO 7 2007 4 7 2776 - + 2007年 [査読有り][通常論文]
     
    An optical coherent manipulation of excitonic polarizations in hexagonal bulk GaN is achieved by means of an interferometric technique combined with spectrally-resolved degenerate four-wave-mixing (FWM). Initial phase of the FWM quantum beats between A and B excitonic polarizations are arbitrarily controlled, in which simultaneous increase (decrease) of the beats in both polarizations are observed. In addition, 80% selective amplification and 40% suppression of one of the excitonic polarizations are realized.
  • T. Ishiguro, Y. Toda, S. Adachi
    APPLIED PHYSICS LETTERS 90 1 011904/1 - 3 2007年01月 [査読有り][通常論文]
     
    The authors studied the exciton spin relaxation of bulk GaN by creating spin polarization gratings using degenerate four-wave mixing spectroscopy. The spectrally resolved analysis achieved with this technique facilitated the direct evaluation of spin polarizations in the individual excitons (A and B excitons). The spin polarizations for each exciton decay very quickly (tau(s)similar to 1 ps) at low temperatures. Moreover the tau(s) is faster than the dephasing time T-2 throughout the measured temperature range, suggesting the existence of fast intrinsic spin relaxation processes, which can be attributed to a large exchange constant characterized in GaN.
  • K. Yamaguchi, Y. Toda, T. Ishiguro, S. Adachi, K. Hoshin, K. Tadatomo
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 4 NO 7 2007 4 7 2752 - + 2007年 [査読有り][通常論文]
     
    Quantum beats in the time-resolved four-wave mixing (FWM) signals arising from GaN excitons are observed. Two different types of beats are investigated: beats between the A-exciton (X-A) and B-exciton (X-B) states; beats between the XA and A-biexciton ((XXA)) states. The former exhibits oscillations along all directions in the delay- (T) and real-time (t) plane while the latter exhibits no beat in the direction parallel to the diagonal axis (T = t). The results are well reproduced by a model calculation, showing good homogeneity of the sample.
  • T Ishiguro, Y Toda, S Adachi, M Arita, Y Arakawa
    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 243 7 1564 - 1567 2006年06月 [査読有り][通常論文]
     
    We have studied exciton spin relaxation in strained GaN epilayers on various sapphire substrates using spin-dependent transient reflectivity and three-pulse four-wave mixing measurements. Strikingly fast exciton spin relaxation (< 1 ps) at 10 K was observed in the lowest exciton level (A-exciton) both in bulk and GaN layer on c-sapphire. In contrast, the transient signals in the GaN layer on alpha-sapphire show the break down of the spin polarization caused by the exchange interaction.
  • T Ishiguro, Y Toda, S Adachi, T Mukai, K Hoshino, Y Arakawa
    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 243 7 1560 - 1563 2006年06月 [査読有り][通常論文]
     
    We have carried out time-integrated and spectrally-resolved four-wave mixing (FWM) measurements to study the effects of built-in strain within GaN films on their exciton structures and on their coherent dynamics. Precise values for exciton energies, linewidths, and oscillation periods of quantum beats were presented. Remarkable phase shifts of the quantum beats were observed in the GaN films on a-sapphire, suggesting the exciton-exciton interaction caused by the reduction of the crystal symmetry.
  • Satoru Adachi, Yasunori Toda, Tetsuro Ishiguro
    PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 243 7 1568 - 1571 2006年06月 [査読有り][通常論文]
     
    Biexcitons of GaN under uniaxial strain have been investigated by spectrally-resolved four-wave mixing (FWM) technique. Two kinds of biexcitons were observed clearly and the binding energies were obtained. Since the uniaxial strain changes the exciton structure, the biexciton binding is modified and biexciton has also fine structure, which was revealed in the FWM spectra that were obtained by rotating the linearly polarized excitation against the direction of uniaxial strain.
  • Hidekazu Kumano, Satoshi Kimura, Michiaki Endo, Ikuo Suemune, Hirotaka Sasakura, Satoru Adachi, Shunichi Muto, Hai Zhi Song, Shinichi Hirose, Tatsuya Usuki
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 32 1-2 144 - 147 2006年05月 [査読有り][通常論文]
     
    Triggered single-photon generation from InAlAs quantum dot (QD) was demonstrated for the first time. Emitted photon energy coincides with high detection efficiency range of Si single-photon detectors, which is highly suitable for free-space communication. Single-QD spectroscopy and crossed photon correlation measurements unambiguously revealed that several emitting lines observed in a single mesa structure originated from the identical QD, and two temporary competing decay processes associated with neutral states and charged states were identified. Presence of the competing process is also inferred from an analysis of steady-state photoluminescence intensities. Formation process of charged exciton in QD is also discussed. (c) 2006 Elsevier B.V. All rights reserved.
  • Hidekazu Kumano, Satoshi Kimura, Michiaki Endo, Hirotaka Sasakura, Satoru Adachi, Shunichi Muto, Ikuo Suemune
    JOURNAL OF NANOELECTRONICS AND OPTOELECTRONICS 1 1 39 - 51 2006年04月 [査読有り][通常論文]
     
    Photon emission with nonclassical photon statistics is discussed with a single InAlAs quantum dot. The deterministic single-photon generation in which the emitted photon wavelength matches well to the highly sensitive wavelength region of highly efficient, low-noise Si-single-photon detectors and also to an atmospheric transmission window is demonstrated. Competing transition processes between neutral and charged exciton species originating from an exclusive formation in the same single quantum dot are clarified. It was found that suppressing the charged exciton formation is possible by a quasi-resonant excitation for a deterministic monochromatic single-photon generation. Polarization-dependent photoluminescence spectroscopy clearly indicates the preservation of photon polarizations between photons emitted by biexciton/exciton recombinations. Furthermore, the deterministic polarization-correlated photon pair generation with biexciton-exciton cascaded transition occurring in a single quantum dot is directly confirmed by the polarized second-order photon correlation measurements. This indicates a longer polarization flip time than the exciton lifetime, which is an essential requirement for the deterministic Einstein-Podolsky-Rosen photon pair generation under the present biexciton-exciton cascaded transition scheme.
  • H. Nishida, S. Kayamori, H. Sasakura, S. Adachi, S. Muto, I. Suemune
    Physica Status Solidi (C) Current Topics in Solid State Physics 3 12 4299 - 4302 2006年 [査読有り][通常論文]
     
    We have investigated the influence of postgrowth thermal annealing on the optical properties of InAs/GaAs self-assembled quantum dots. Upon annealing, the emission from InAs QDs shifts toward higher energies with a narrowing of the photoluminescence spectra of QD ensemble. The time-integrated PL spectra show also the nonradiative recombination rate does not increase by annealing process. In addition, from the timeresolved PL, the exciton radiative recombination rate increases with increasing the annealing temperature and agrees well with the atomic-like radiative recombination. These results indicate that interdiffusion of Ga and In atoms into and out of the QDs leads to an increase of the average dot size and concurrently a decrease in the confinement potentials of the QDs preserving their optical quality and zero-dimensional density of states after interdiffusion in the studied annealing temperature range. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.
  • T. Mukumoto, R. Kaji, H. Sasakura, S. Adachi, H. Kumano, S. Muto, I. Suemune
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 12 3 12 4372 - 4375 2006年 [査読有り][通常論文]
     
    We report optical pumping of nuclear spin polarization in a single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dot where the exciton has a fine structure. Through the change of state mixing that is induced by the anisotropic exchange interaction and the applied magnetic field, the relationship between the magnitude of the Overhauser shift and the optically injected electron spin polarization is discussed. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • Shinji Abe, Hirotaka Sasakura, Satoru Adachi, Shunichi Muto
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 12 3 12 4295 - 4298 2006年 [査読有り][通常論文]
     
    We have investigated the pulse parameters of the stimulated Raman adiabatic passage (STIRAP) for efficient electron transfer in the coupled quantum dot system, and we found that STIRAP is sensitive to the difference between the dipole moments of the involved transitions. We have designed the QD structures where this drawback can be suppressed, to show the practicality of the photon-assisted tunneling between spatially-separated QDs. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • Satoru Adachi, Yasunori Toda, Tetsuro Ishiguro, Katsuyuki Hoshino, Yasuhiko Arakawa
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 6 3 6 1595 - 1598 2006年 [査読有り][通常論文]
     
    Exciton fine structures induced by the uniaxial strain have been revealed in gallium nitride grown on an a-plane sapphire substrate by using the spectrally-resolved four-wave mixing technique. Sensitivity on the exciton polarization is enhanced by the nonlinearities of the four wave mixing signals, and therefore the safety alternative tool for mapping of the uniaxial strain field and the resultant anisotropic exchange can be offered. Such a nonlinear spectroscopic measurement gives a kind of crystalline analysis achieved in X-ray diffraction spectroscopy as well as information of the exciton fine structures including their temporal dynamics. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • I. Suemune, H. Kumano, S. Kimura, H. Sasakura, S. Adachi, S. Muto, H. Z. Song, S. Hirose, T. Usui
    PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 3, NO 11 3 11 3908 - + 2006年 [査読有り][通常論文]
     
    It is well-recognized that exciton-state energy splitting makes it difficult to generate entangled photon pairs (EPP) from a single quantum dot (QD). It will be shown that the splitting of the exciton states originates from not only QD anisotropy but also ionization of residual impurities. This result shows that the growth of highly pure barrier layers will be necessary for the generation of EPP. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • T Yokoi, S Adachi, S Muto, H Sasakura, HZ Song, S Hirose, T Usuki
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 29 3-4 510 - 514 2005年11月 [査読有り][通常論文]
     
    We report the polarization-dependent energy shift of excitonic emission in a self-assembled InAlAs/AlGaAs quantum dot (QD). The energy shift is well known as Overhauser shift and was observed in a naturally formed GaAs QD using monolayer fluctuation of a quantum well. However, there has been no observation so far in a self-assembled QD, which is suitable for formation of vertically coupled QDs. We demonstrate that the magnitude of the Overhauser shift is enhanced by the photo-injection of the highly polarized electron and is controllable by the polarization of the excitation light in a self-assembled InAlAs QD. (c) 2005 Elsevier B.V. All rights reserved.
  • S Muto, S Adachi, T Yokoi, H Sasakura, Suemune, I
    APPLIED PHYSICS LETTERS 87 11 112506/1 - 3 2005年09月 [査読有り][通常論文]
     
    We propose a method to realize the conversion of photon qubit and spin qubit using the effective magnetic field created by the nuclear polarization known as Overhauser field. We discuss the preliminary experiment on an InAlAs/AlGaAs self-assembled quantum dot and also discuss the effects of electron-hole interaction on the conversion. (c) 2005 American Institute of Physics.
  • Y Toda, S Adachi, Y Abe, K Hoshino, Y Arakawa
    PHYSICAL REVIEW B 71 19 195315/1 - 5 2005年05月 [査読有り][通常論文]
     
    The degenerate four-wave mixing (FWM) spectroscopy of uniaxially strained GaN layers is demonstrated using colinearly polarized laser pulses. The nonlinear response of FWM signal on exciton oscillator strength enhances the sensitivity for polarized exciton, allowing for mapping out the in-plane anisotropy of the strain field. The observed high-contrast spectral polarization clearly shows fine structure splittings of excitons, which are also confirmed in the change of quantum beating periods of time.
  • S Adachi
    JOURNAL OF LUMINESCENCE 112 1-4 34 - 39 2005年04月 [査読有り][通常論文]
     
    We have investigated free excitons and biexcitons of bulk ZnO by time-integrated and spectrally resolved four-wave mixing (FWM). The polarization- and wave-vector-dependent FWM signals for A and B excitons demonstrate clearly that the valence-band ordering is A-Gamma(9), B-Gamma(7), and C-Gamma(7). Also, we gave qualitative explanation of the FWM signals induced by excitons and biexcitons in ZnO. For negative delay times, bound and unbound AB-biexcitons (A exciton-B exciton correlation), which have been considered to play a minor role in GaAs hetero structures, was found to play an important role and give a significant qualitative impact to the optical response of ZnO. (c) 2004 Elsevier B.V. All rights reserved.
  • K Hazu, S Adachi, T Sota, SF Chichibu
    JOURNAL OF LUMINESCENCE 112 1-4 7 - 10 2005年04月 [査読有り][通常論文]
     
    We have studied the exciton-polariton dynamics in a c-face bulk ZnO crystal grown by the seeded vapor transport method. We have performed two-pulse spectrally resolved four-wave mixing (SR-FWM) and three-pulse SR-FWM at T = 10 K. In two-pulse FWM experiment, obtained FWM signals showed the fast dephasing which has been attributed to the strong polariton dispersion of the upper polariton of B exciton. On the other hand, in three-pulse FWM experiment, the signal decay shows the free exciton population relaxation. Observed FWM signal has decayed with time constant similar to 12 ps which may represent exciton-polariton lifetime. (c) 2004 Elsevier B.V. All rights reserved.
  • T Watanuki, S Adachi, H Sasakura, S Muto
    APPLIED PHYSICS LETTERS 86 6 063114/1 - 3 2005年02月 [査読有り][通常論文]
     
    Exciton spin relaxation in self-assembled InAlAs quantum dots was investigated by three-pulse four-wave mixing under resonant conditions. The concept of the spin grating holds well for quantum dots and the measurements combined with optical heterodyne detection at 10 K demonstrates that the exciton spin relaxation lasts up to a few nanoseconds and the time constant is similar to5 times larger than the exciton recombination time on average. (C) 2005 American Institute of Physics.
  • S Adachi, Y Toda
    PHYSICA STATUS SOLIDI C - CONFERENCES AND CRITICAL REVIEWS, VOL. 2 , NO 11 2 11 3936 - 3940 2005年 [査読有り][通常論文]
     
    Spectrally-resolved four-wave mixing technique has revealed the internal structures of excitons in uniaxially strained gallium nitride films. Nonlinear response of four-wave mixing on the oscillator strength highlights the polarized excitons, and therefore allows us to map out the uniaxial strain field and the resultant anisotropic exchange splitting. Such a measurement gives a kind of crystalline analysis achieved in X-ray diffraction spectroscopy as well as information of the exciton fine structures including their temporal dynamics.
  • S Kimura, H Kumano, M Endo, Suemune, I, T Yokoi, H Sasakura, S Adachi, S Muto, HZ Song, S Hirose, T Usuki
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 44 24-27 L793 - L796 2005年 [査読有り][通常論文]
     
    Single-photon emitters and detectors are key devices to realize secure communications with single-photon-based quantum cryptography and single-photon-based quantum computing. InAlAs quantum dots (QDs) cover the wavelength range with high quantum efficiencies of Si-based single-photon detectors. Clear photon antibunching was observed from an InAlAs single QD under weak excitations. To realize single-photon emitters on demand, complete population of the QD energy states before the photon emission events is necessary, but the measured antibunching properties were dependent substantially on the photo-excitation powers. The physical origin of this problem is discussed. The criterion to distinguish the real deviation from the photon antibunching condition and the artifact of the measurements is clarified. The capability of single-photon emissions on demand will be demonstrated with photon antibunching under pulsed operations.
  • S Kimura, H Kumano, M Endo, Suemune, I, T Yokoi, H Sasakura, S Adachi, S Muto, HZ Song, S Hirose, T Usuki
    PHYSICA STATUS SOLIDI C - CONFERENCES AND CRITICAL REVIEWS, VOL. 2 , NO 11 2 11 3833 - 3837 2005年 [査読有り][通常論文]
     
    Regulated single-photon generation from an InAlAs quantum dot was demonstrated at a wavelength in which Si-avalanche photodiode single-photon detector has high quantum efficiency. Measured excitation power dependence of photon coincidence counts revealed that highly pure single-photon emission was realized at low excitation powers. Beyond a critical excitation, population of multi-exciton states in the quantum dot degraded the purity of single-photon emission. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • S Adachi, K Hazu, T Sota, S Chichibu, G Cantwell, DC Reynolds, CW Litton
    FOURTH INTERNATIONAL CONFERENCE ON PHYSICS OF LIGHT-MATTER COUPLING IN NANOSTRUCTURES (PLMCN4) 2 2 890 - 895 2005年 [査読有り][通常論文]
     
    We have investigated free excitons and biexcitons of bulk ZnO by time-integrated and spectrally-resolved four-wave mixing. The polarization- and wave-vector-dependent FWM signals for A and B excitons demonstrate clearly that the valence-band ordering is A - Gamma(9), B - Gamma(7), and C - Gamma(7). Next, we gave qualitative explanation of the FWM signals induced by excitons and biexcitons in ZnO. For negative delay times, bound and unbound AB-biexcitons (A exciton-B exciton correlation), which have been considered to play a minor role in GaAs heterostructures, was found to play an important role and give a significant qualitative impact to the optical response of ZnO. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • S Adachi, T Watanuki, H Sasakura, S Muto
    Fourth International Conference on Physics of Light-Matter Coupling in Nanostructures (PLMCN4) 2 2 854 - 857 2005年 [査読有り][通常論文]
     
    Exciton spin relaxation in self-assembled InAlAs quantum dots were investigated by three-pulse four-wave mixing under resonant conditions. The concept of the spin grating holds well for quantum dots and the measurements combined with optical heterodyne detection at 10 K demonstrates that the exciton spin relaxation last up to a few ns and the time constant is similar to 5 times larger than the exciton recombination time in average. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • T Yokoi, S Adachi, H Sasakura, S Muto, HZ Song, T Usuki, S Hirose
    PHYSICAL REVIEW B 71 4 R041307/1 - 4 2005年01月 [査読有り][通常論文]
     
    We report optical spectroscopic results of a single self-assembled In0.75Al0.25As/Al0.3Ga0.7As quantum dot. The polarization-dependent shift of the Zeeman splitting in a single InAlAs quantum dot (QD) has been observed. The induced Overhauser field is estimated to be similar to0.16 T in this InAlAs QD and the magnitude is shown to be controllable by the degree of circular polarization of excitation light.
  • S Adachi, T Yokoi, H Sasakura, S Muto, H Kumano, Suemune, I
    PHYSICA STATUS SOLIDI C - CONFERENCES AND CRITICAL REVIEWS, VOL. 2 , NO 11 2 11 3838 - 3842 2005年 [査読有り][通常論文]
     
    We present the signature for optical pumping of nuclear spins in a self-assembled InAlAs/AlGaAs quantum dot via the polarization-dependent energy shift of the excitonic emission. The energy shift is well known as Overhauser shift and has observed in a interface-fluctuation GaAs quantum dot. However, there has been no observation so far in a self-assembled QD, which is suitable for formation of vertically coupled QDs. We have demonstrated that the magnitude of the Overhauser shift was enhanced by the photo-injection of the highly-polarized electron and was controllable by the polarization of the excitation light. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Satoru Adachi, Tomonori Yokoi, Hirotaka Sasakura, Shunichi Muto, Hidekazu Kumano, Ikuo Suemune
    Physica Status Solidi C: Conferences 2 11 3838 - 3842 2005年 [査読有り][通常論文]
     
    We present the signature for optical pumping of nuclear spins in a self-assembled InAlAs/AlGaAs quantum dot via the polarization-dependent energy shift of the excitonic emission. The energy shift is well known as Overhauser shift and has observed in a interface-fluctuation GaAs quantum dot. However, there has been no observation so far in a self-assembled QD, which is suitable for formation of vertically coupled QDs. We have demonstrated that the magnitude of the Overhauser shift was enhanced by the photo-injection of the highly-polarized electron and was controllable by the polarization of the excitation light. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • S. Kimura, H. Kumano, M. Endo, I. Suemune, T. Yokoi, H. Sasakura, S. Adachi, S. Muto, H. Z. Song, S. Hirose, T. Usuki
    Physica Status Solidi C: Conferences 2 11 3833 - 3837 2005年 [査読有り][通常論文]
     
    Regulated single-photon generation from an InAlAs quantum dot was demonstrated at a wavelength in which Si-avalanche photodiode single-photon detector has high quantum efficiency. Measured excitation power dependence of photon coincidence counts revealed that highly pure single-photon emission was realized at low excitation powers. Beyond a critical excitation, population of multi-exciton states in the quantum dot degraded the purity of single-photon emission. ©2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • Satoru Adachi, Yasunori Toda
    Physica Status Solidi C: Conferences 2 11 3936 - 3940 2005年 [査読有り][通常論文]
     
    Spectrally-resolved four-wave mixing technique has revealed the internal structures of excitons in uniaxially strained gallium nitride films. Nonlinear response of four-wave mixing on the oscillator strength highlights the polarized excitons, and therefore allows us to map out the uniaxial strain field and the resultant anisotropic exchange splitting. Such a measurement gives a kind of crystalline analysis achieved in X-ray diffraction spectroscopy as well as information of the exciton fine structures including their temporal dynamics. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
  • K Hazu, T Sota, S Adachi, S Chichibu, G Cantwell, DC Reynolds, CW Litton
    JOURNAL OF APPLIED PHYSICS 96 2 1270 - 1272 2004年07月 [査読有り][通常論文]
     
    The phase relaxation time of biexcitons T-2(bi) and that of excitons T-2(ex) in a bulk ZnO have been measured by the use of femtosecond four-wave mixing as functions of excitation wavelength, excitation power, and temperature. The biexciton-acoustic phonon interaction coefficient has been determined to be beta(ac)(bi)approximate to53 mueV/K as an average value. For A excitons, the interaction coefficients with acoustic and optical phonons have been determined to be beta(ac)(ex)approximate to8.4 mueV/K and beta(opt)(ex)approximate to14 meV, respectively. (C) 2004 American Institute of Physics.
  • K Hazu, K Torii, T Sota, S Adachi, SF Chichibu, G Cantwell, DC Reynolds, CW Litton
    JOURNAL OF APPLIED PHYSICS 95 10 5498 - 5501 2004年05月 [査読有り][通常論文]
     
    Time-integrated and spectrally resolved four-wave mixing (FWM) has been applied to study the impact of the k-linear term on nonlinear optical response of the C-exciton manifold in ZnO. From the excitation wavelength dependence of the FWM signal, we have found possible evidence that the mixing of the Gamma(1) and Gamma(5L) states leads to a three-branch excitonic polariton dispersion but the oscillator strength transfer is small. The energy separation between the lower polariton branch and the extra branch due to the k-linear term has been found to be 3.5 meV. In addition, a binding energy of biexcitons consisting of two C excitons of 1.4 meV has been obtained. (C) 2004 American Institute of Physics.
  • S Adachi, K Hazu, T Sota, SF Chichibu, G Cantwell, DB Eason, DC Reynolds, CW Litton
    SEMICONDUCTOR SCIENCE AND TECHNOLOGY 19 4 S276 - S278 2004年04月 [査読有り][通常論文]
     
    We demonstrate that exciton-exciton correlations strongly affect FWM signals. In particular, A exciton-B exciton correlation (bound and unbound A B-biexcitons), which can be generated even in co-circular polarizations, has a significant qualitative impact on the optical response of bulk ZnO.
  • H Sasakura, S Adachi, S Muto, T Usuki, M Takatsu
    SEMICONDUCTOR SCIENCE AND TECHNOLOGY 19 4 S409 - S411 2004年04月 [査読有り][通常論文]
     
    We have studied the various types of Coulomb interactions in triple quantum dots and estimated their effects on the gate operation of quantum computation. In view of the magnitude of the Coulomb energies, the system requirements for error-free and high-speed operation are discussed.
  • H Sasakura, S Adachi, S Muto, HZ Song, T Miyazawa, T Usuki
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 43 4B 2110 - 2113 2004年04月 [査読有り][通常論文]
     
    Time-resolved photoluminescence experiments have been performed to investigate exciton spin relaxation processes at low temperatures in InAlAs-InGaAs asymmetric double quantum dots embedded in AlGaAs layers. By decreasing the thickness of the AlGaAs barrier between the dots, the spin relaxation times decreased from 3 ns to 1 ns. The observed spin relaxation as a function of barrier thickness was reasonably described by two components: one was a constant and the other was exponentially depended on barrier thickness. The origin of the latter component is discussed in connection with spin-flip tunneling.
  • H Sasakura, S Adachi, S Muto, HZ Song, T Miyazawa, Y Nakata
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 21 2-4 511 - 515 2004年03月 [査読有り][通常論文]
     
    Exciton spin relaxation at low temperatures in InAlAs-InGaAs asymmetric double quantum dots embedded in AlGaAs layers has been investigated as a function of the barrier thickness by the time-resolved photoluminescence measurements. With decreasing the thickness of the AlGaAs layer between the dots, the spin relaxation time change from 3 ns to less than 500 ps. The reduction in the spin relaxation time was considered to originate from the spin-flip tunneling between the ground state in InAlAs dot and the excited states in InGaAs dot, and the resultant tunneling leads to the spin depolarization of the ground state in InGaAs dot. (C) 2003 Elsevier B.V. All rights reserved.
  • S Adachi, H Sasakura, S Muto, K Hazu, T Sota, SK Chichibu, T Mukai
    PHYSICA STATUS SOLIDI B-BASIC RESEARCH 240 2 348 - 351 2003年11月 [査読有り][通常論文]
     
    Bound and unbound biexcitons in a free-standing, bulk GaN are investigated by time-integrated and spectrally-resolved four-wave mixing measurements, where the formation of hetero-biexcitons that consist of A and B excitons (XXAB) as well as A biexcitons and their unbound biexciton are clearly observed. Through the FWM spectra and delay-time dependence, it is found that the interaction between A and B excitons gives rise to the phase shifts of the quantum beating and the energy shifts of the spectra, which is considered as the effect of the unbound state of XXAB (i.e. XX*(AB)). This interaction is found to play an important role in the FWM signals for all polarizations. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.
  • H Sasakura, S Adachi, S Muto
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 42 10 6308 - 6313 2003年10月 [査読有り][通常論文]
     
    Quantum computation using electron spins in three-coupled dots of different sizes is proposed. By using photon-assisted tunnelling, Coulomb blockade and spin rotation of electrons, logic gates are realized by static and rotational magnetic fields and resonant optical pulses. The two-bit CNOT is numerically demonstrated by the time evolution of the density matrix. In addition, the Hamiltonian is described using pseudo-spin representation and the phase change during the gate operation is discussed.
  • K. Hazu, T. Sota, K. Suzuki, S. Adachi, S. F. Chichibu, G. Cantwell, B. Eason, C. Reynolds, W. Litton
    Physical Review B - Condensed Matter and Materials Physics 68 11 2003年07月15日 [査読有り][通常論文]
     
    We have studied experimentally biexcitonic states of ZnO of rather high quality in the low exciton density limit by means of time-integrated and spectrally-resolved four-wave mixing (FWM). FWM emission signals due to biexcitons consisting of two A-hole excitons (AA biexcitons), an A-hole and a B-hole exciton (AB biexcitons), and two B-hole excitons (BB biexcitons) have been clearly observed according to polarization selection rules. The obtained binding energies for AA, AB, and BB biexcitons are 15.6, 16.6, and 4.7 meV, respectively. A brief discussion is also given on the contribution of biexciton and two-pair continuum resonances to the FWM signal. © 2003 The American Physical Society.
  • K Hazu, T Sota, K Suzuki, S Adachi, SF Chichibu, G Cantwell, DB Eason, DC Reynolds, CW Litton
    PHYSICAL REVIEW B 68 3 033205/1 - 4 2003年07月 [査読有り][通常論文]
     
    We have studied experimentally biexcitonic states of ZnO of rather high quality in the low exciton density limit by means of time-integrated and spectrally-resolved four-wave mixing (FWM). FWM emission signals due to biexcitons consisting of two A-hole excitons (AA biexcitons), an A-hole and a B-hole exciton (AB biexcitons), and two B-hole excitons (BB biexcitons) have been clearly observed according to polarization selection rules. The obtained binding energies for AA, AB, and BB biexcitons are 15.6, 16.6, and 4.7 meV, respectively. A brief discussion is also given on the contribution of biexciton and two-pair continuum resonances to the FWM signal.
  • O Ikeuchi, S Adachi, H Sasakura, S Muto
    JOURNAL OF APPLIED PHYSICS 93 12 9634 - 9638 2003年06月 [査読有り][通常論文]
     
    We observed the exciton spin dynamical processes in GaAs quantum wells at low temperatures by three-pulse spin-diffracted four-wave mixing measurements. After investigating the merits and demerits of this method as compared with the pump-probe method, we discuss the excitation power dependence of exciton spin relaxation and the population transfer to the dark states. (C) 2003 American Institute of Physics.
  • S Adachi, S Muto, K Hazu, T Sota, K Suzuki, SF Chichibu, T Mukai
    PHYSICAL REVIEW B 67 20 205212/1 - 5 2003年05月 [査読有り][通常論文]
     
    The formation of not only A biexcitons (XXAA) but also heterobiexcitons that consist of A and B excitons (XXAB) in a free-standing bulk GaN is identified by polarization-sensitive spectrally resolved FWM measurements. The FWM spectra and delay-time dependence show that the interaction between A and B exciton gives rise to the energy shifts of the spectra and the phase shifts of the quantum beating, which is considered as the effect of the unbound state of XXAB (i.e., XXAB*) and XXAB* is found to play an important role in the FWM signals for all polarizations. The unbound A biexciton (XXAA*) is also observed clearly in spectral and temporal domains.
  • K Hazu, T Sota, K Suzuki, S Adachi, S Chichibu
    ULTRAFAST PHENOMENA IN SEMICONDUCTORS VII 4992 257 - 264 2003年 [査読無し][通常論文]
     
    Time-integrated and spectrally-resolvd four-wave mixing (FWM) has been used to study dephasing dynamics of excitons in a free-standing bulk ZnO. Clear FWM signals due to AGamma(5)- and BGamma(5)-excitons have been observed. We discuss the dephasing dynamics based on the polariton dispersion and four-particle Coulomb correlations.
  • S Adachi, K Hazu, T Sota, SF Chichibu, T Mukai, S Muto, K Suzuki
    ULTRAFAST PHENOMENA IN SEMICONDUCTORS VII 4992 188 - 201 2003年 [査読無し][通常論文]
     
    Bound and unbound biexcitons in a free-standing bulk GaN are investigated by time-integrated and spectrally-resolved four-wave mixing measurements, where the formation of hetero-biexcitons that consist of A and B excitons (XXAB) as well as A-biexcitons (XXAA) and their unbound biexciton (XXAA*) are clearly observed. The FWM spectra and delay-time dependence are explained qualitatively and the interaction between A- and B-excitons gives rise to the phase shifts of the quantum beating and the energy shifts of the spectra, which is considered as the effect of the unbound state of XXAB (i.e. XXAB*). The unbound A-biexciton (XXAA*) is also observed clearly in spectral and temporal domain and is found to play an important role in FWM signals for all polarizations.
  • S Adachi, S Maki, O Ikeuchi, H Sasakura, S Muto
    ULTRAFAST PHENOMENA IN SEMICONDUCTORS VII 4992 241 - 248 2003年 [査読有り][通常論文]
     
    We have observed the exciton spin relaxation processes in GaAs quantum wells at low temperatures by three-pulse spin-diffracted four-wave mixing measurements. After investigating the merits and demerits of this new method as compared with the pump-probe technique, we discuss the population transfer to the dark states through the measurements of the excitation-power dependence of exciton spin relaxation. Spin-diffracted four-wave mixing method is a powerful tool to investigate exciton spin dynamical processes where the pump-probe and time-resolved photoluminescence measurements have been used so far, since the method can be used in reflection geometry and be applicable to thin films and quantum dots.
  • K. Hazu, A. Shikanai, T. Sota, K. Suzuki, S. Adachi, S. F. Chichibu, T. Mukai
    Physical Review B - Condensed Matter and Materials Physics 65 19 1952021 - 1952028 2002年05月15日 [査読有り][通常論文]
     
    We have studied the properties of coherent exciton states in a free standing wurtzite GaN using the degenerate four-wave-mixing (FWM) technique with subpicosecond time resolution. The polarization dependence of spectrally resolved FWM signals has demonstrated that excitation-induced dephasing is the dominant FWM process. The exciton energy renormalization has been found to dependent on the polarization configuration. FWM signals due to local field effect have been successfully discriminated from those due to other effects. These reveal an importance of four-particle correlations in two-exciton continuum states even for the low excitation power limit where no bound biexciton signal is detected. The temperature dependence of the homogeneous broadening of excitons has also been studied up to 60 K, to obtain the exciton-acoustic phonon interaction coefficient of 9 μeV/K.
  • K Hazu, A Shikanai, T Sota, K Suzuki, S Adachi, SF Chichibu, T Mukai
    PHYSICAL REVIEW B 65 19 195202/1 - 8 2002年05月 [査読有り][通常論文]
     
    We have studied the properties of coherent exciton states in a free standing wurtzite GaN using the degenerate four-wave-mixing (FWM) technique with subpicosecond time resolution. The polarization dependence of spectrally resolved FWM signals has demonstrated that excitation-induced dephasing is the dominant FWM process. The exciton energy renormalization has been found to dependent on the polarization configuration. FWM signals due to local field effect have been successfully discriminated from those due to other effects. These reveal an importance of four-particle correlations in two-exciton continuum states even for the low excitation power limit where no bound biexciton signal is detected. The temperature dependence of the homogeneous broadening of excitons has also been studied up to 60 K, to obtain the exciton-acoustic phonon interaction coefficient of 9 mueV/K.
  • S Muto, H Sasakura, S Adachi, Y Kajiwara, K Shiramine
    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES 13 2-4 616 - 619 2002年03月 [査読有り][通常論文]
     
    Quantum gates using tunneling qubits: tunneling of electrons whose spins work as qubits is described by the Hamiltonian using both electron spins and pseudo-spins representing the photon-assisted tunneling. The phase factor during the controlled-NOT operation is also discussed. Preliminary data on a triple quantum dot system realized by closely stacking technique of molecular beam epitaxy are also shown. (C) 2002 Elsevier Science B.V. All rights reserved.
  • S Adachi, T Tsuchiya, H Mino, S Takeyama, G Karczewski, T Wojitowicz, J Kossut
    PHYSICA E 10 1-3 305 - 309 2001年05月 [査読有り][通常論文]
     
    Exciton and biexciton optical properties in II-VI semiconductor single quantum well have been studied by magneto-photoluminescence, and time-resolved four-wave-mixing spectroscopies. The polarization dependence of both measurements can clearly distinguish biexciton from other bound states and show the dynamical spin properties of exciton and biexciton. (C) 2001 Elsevier Science B.V. All rights reserved.
  • H Mino, S Takeyama, S Adachi, G Karczewski, T Wojtowicz, J Kossut
    PHYSICA B 298 1-4 421 - 425 2001年04月 [査読有り][通常論文]
     
    An exciton and a biexciton photoluminescence in (Cd,Mn)Te/CdTe/(Cd,Mg)Te asymmetric quantum wells were investigated under magnetic fields. A quantum beat between an exciton and a biexciton has been observed by a transient four-wave-mixing spectroscopy. The spin-energy structures have been clarified by spectra of the four-wave-mixing signals. We have observed decrease of the intensity ratio of a biexciton to an exciton on increasing magnetic field. The instability of the spin singlet biexciton state is determined by the inner effective magnetic field produced by the local Mn magnetic moments. (C) 2001 Elsevier Science B.V. All rights reserved.
  • S Takeyama, S Adachi, Y Takagi
    PHASE TRANSITIONS 74 1-2 175 - 207 2001年 [査読有り][通常論文]
     
    Exciton magnetic polarons observed in dilute magnetic semiconductors were investigated by steady-state and pico-second time-resolved photoluminescence measurements and have shown characteristic behavior of exciton localization processes in bulk Cd1-xMnxTe and also in the quantum structures composed of the dilute magnetic semiconductors. For the quantum structures spin-dependent coherent polarizations associated with excitons and biexcitons were studied by degenerate four-wave mixing experiment. Also investigated for different chalcogenide spinel ferromagnetic semiconductors was photo-induced enhancement of exchange interaction between magnetic ions by direct magnetic flux detection in the vicinity of the Curie temperatures.
  • S Takeyama, H Mino, S Adachi, T Stirner, WE Hagston, H Yokoi, YG Semenov, SW Tozer, Y Kim, G Karczewski, J Kossut
    PHYSICA B 294 453 - 458 2001年01月 [査読有り][通常論文]
     
    Exciton photoluminescence in a diluted magnetic asymmetric quantum well has given clear evidence of "asymmetric exciton magnetic polaron states" in magnetic fields. The theoretical calculation to interpret the observed magneto-optical data has clarified the importance of exciton localization associated with the interface disorder and the alloy potential fluctuation in addition to the exciton magnetic polaron formation in the asymmetric diluted magnetic barrier. The possibility of a "bifurcated" exciton states is discussed. The transient four-wave-mixing nonlinear spin selective optical measurements revealed the spin-structure of excitons and biexcitons in diluted magnetic quantum structures. The effects of the magnetic field on biexciton states have been investigated. The photoluminescence transition from the biexciton to exciton states has been investigated in magnetic fields, and the stability of the biexciton states in either bonding (spin singlet) or anti-bonding states (spin triplet) is discussed. We have proposed methods to deduce the interface magnetism in the diluted magnetic quantum structures from the high-field Zeeman splitting of exciton photoluminescence up to 60 T. (C) 2001 Elsevier Science B.V. All rights reserved.
  • S. Adachi, S. Muto, K. A. Nelson
    Technical Digest - Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference, QELS 2001 208  2001年 [査読有り][通常論文]
     
    Summary form only given. In order to investigate the relation between particle diffusion and spin diffusion, we used polarization-dependent transient gratings, an exciton density grating and an exciton spin grating, in optical sampling four-wave mixing measurements (OSFWM), which allows us to measure both particle and spin diffusion in the same system. Because OSFWM has a wide observable temporal range from sub-ps to 13 ns with 200-fs temporal resolution, long recombination is possible to observe, and therefore we can compare directly both diffusions. The sample investigated consists of 25 periods of undoped 68-Å-thick GaAs quantum wells (QWs), alternated with 198-Å-thick Al0.3Ga0.7As barrier layers. The sample was grown on a semi-insulating [100]-GaAs substrate by molecular beam epitaxy.
  • S Adachi, Y Takagi, S Takeyama
    JOURNAL OF CRYSTAL GROWTH 214 819 - 822 2000年06月 [査読有り][通常論文]
     
    We have performed two-pulse and three-pulse time-integrated as well as spectrally resolved four-wave-mixing measurements on a single CdMnTe/CdTe/CdMgTe quantum well. The polarization dependence of both four-wave-mixing measurements can be explained well by the five-level model of the exciton-biexciton system including two-biexciton states with parallel spin and anti-parallel spin orientations. (C) 2000 Elsevier Science B.V. All rights reserved.
  • S Adachi, RM Koehl, KA Nelson
    JOURNAL OF LUMINESCENCE 87-9 840 - 843 2000年05月 [査読有り][通常論文]
     
    Coherent optic phonon-polaritons generated through impulsive stimulated Raman scattering in a ferroelectric crystal are imaged with 5-mu m spatial resolution and 35-fs time resolution. This imaging spectroscopy allows us to perform direct measurement of space- and time-dependent response function induced by the propagating phonon-polaritons. The method will also permit direct examination of nonlinear lattice dynamics and will provide feedback: in coherent control system. (C) 2000 Elsevier Science B.V. All rights reserved.
  • S. Adachi, Y. Takagi, J. Takeda, K. A. Nelson
    Optics Communications 174 1-4 291 - 298 2000年01月15日 [査読有り][通常論文]
     
    We have developed the optical sampling four-wave mixing technique applicable to measurements of the ultrafast dynamical processes in liquid and solid materials. The method is examined to reveal the exciton dynamical processes in GaAs quantum wells at low temperatures. By using the optical sampling principle, this new spectroscopic tool provides well timing-controlled two-color light pulses for excitation and detection, and also wide observable temporal range from sub-picoseconds to a few nanoseconds with femtosecond time resolution. Various transient processes such as phase relaxation, spin relaxation, and energy relaxation processes can therefore be observed rapidly in the common measurement system.
  • S Adachi, Y Takagi, J Takeda, KA Nelson
    OPTICS COMMUNICATIONS 174 1-4 291 - 298 2000年01月 [査読有り][通常論文]
     
    We have developed the optical sampling four-wave mixing technique applicable to measurements of the ultrafast dynamical processes in liquid and solid materials. The method is examined to reveal the exciton dynamical processes in GaAs quantum wells at low temperatures. By using the optical sampling principle, this new spectroscopic tool provides well timing-controlled two-color light pulses for excitation and detection, and also wide observable temporal range from sub-picoseconds to a few nanoseconds with femtosecond time resolution. Various transient processes such as phase relaxation, spin relaxation, and energy relaxation processes can therefore be observed rapidly in the common measurement system. (C) 2000 Elsevier Science B.V. All rights reserved.
  • RM Koehl, S Adachi, KA Nelson
    JOURNAL OF PHYSICAL CHEMISTRY A 103 49 10260 - 10267 1999年12月 [査読有り][通常論文]
     
    Direct spatiotemporal imaging of optic phonon-polariton wavepackets in polar crystals is demonstrated experimentally and described theoretically. Spatiotemporal imaging permits monitoring of wavepackets as they move through host samples at lightlike speeds. Different imaging methods may be used optimally for wavepackets with different spatial distributions, including spatially periodic or nonperiodic wavepackets. Spatiotemporal imaging holds particular promise for coherent phonon-polariton wavepacket control using spatiotemporal femtosecond pulse shaping.
  • S Takeyama, S Adachi, Y Takagi, G Karczewski, T Wojtowicz, J Kossut, T Karasawa
    MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY 63 1-2 111 - 118 1999年08月 [査読有り][通常論文]
     
    The temperature dependence of exciton magnetic polaron energies was determined from the pico-second time-resolved photoluminescence (PL) spectra, and have shown characteristic dynamical behavior of exciton localization process in bulk-Cd(1-)xMn(x)Te (x = 0.1-0.2). The overall behavior appears different from that reported previously for the bound- or localized-exciton magnetic polarons (EMP) in the same material. In symmetric diluted magnetic semiconductor (DMS) quantum wells (QWs), CdTe/Cd1-xMnxTe, studied here by steady-state and transient-PL, it is plausible that the exciton magnetic polaron formation occurs after localization by the nonmagnetic disorders. Temperature and magnetic-field dependencies (up to 15 T) of PL have been studied in Cd1-xMnxTe - CdTe-Cd1-yMgyTe asymmetric single QWs. These show the phenomena similar to those expected in the exciton 'bifurcation' effect due to magnetic polaron formation on one side of the diluted magnetic barrier. The doublet PL lines observed are attributed to symmetric and asymmetric exciton states. Biexcitons are observed in DMS-QWs, and confirmed by the polarized two-pulse degenerate four-wave-mixing (DFWM) experiment. (C) 1999 Published by Elsevier Science S.A. All rights reserved.
  • Y Takagi, S Adachi
    REVIEW OF SCIENTIFIC INSTRUMENTS 70 5 2218 - 2224 1999年05月 [査読有り][通常論文]
     
    We have developed a subpicosecond nondegenerate pump-probe spectrometer based on the optical sampling technique using a combination of asynchronous tunable femtosecond lasers. Owing to its simple instrumentation, time evolution of subpicosecond to nanosecond excited molecular processes in solution and of exciton relaxation processes in semiconductor multiple quantum wells has been detected on an oscilloscope by an effective time base magnification of 760 000 times. Fast acquisition of the temporal profiles and ease of wavelength scanning allowed compilation of time-resolved absorption and excitation spectra. A possible extention of the spectrometer with one of the light sources being a synchrotron radiation instead of the femtosecond laser is discussed. (C) 1999 American Institute of Physics. [S0034-6748(99)03005-1].
  • RM Koehl, S Adachi, KA Nelson
    JOURNAL OF CHEMICAL PHYSICS 110 3 1317 - 1320 1999年01月 [査読有り][通常論文]
     
    The propagation of collective lattice vibrational wave packets that move at lightlike speeds through their crystalline hosts has been monitored through a real-space imaging method based on Fresnel diffraction and phase-contrast microscopy. Coherent optic phonon-polaritons generated through impulsive stimulated Raman scattering in a ferroelectric crystal are imaged with 5 mu m spatial resolution and 35 fs time resolution as they propagate out of the excitation region and into other parts of the crystal. The "spatiotemporal'' imaging method will permit direct examination of nonlinear lattice dynamics and will provide feedback in coherent control systems that use spatiotemporal femtosecond pulse shaping to manipulate propagating excitations with ultrashort light pulses directed to specified sample locations at specified times. The method will also permit the examination of defects and fabricated structures in bulk or thin film crystals using visible light. (C) 1999 American Institute of Physics. [S0021-9606(99)01803-6].
  • S Adachi, Y Takagi
    PHYSICS OF LOW-DIMENSIONAL STRUCTURES 1-2 133 - 142 1998年 [査読有り][通常論文]
     
    We observed the exciton spin dynamical processes in the nonlinear polarization-dependent pump-probe measurements of GaAs/AlGaAs quantum wells and compared the results at low and room temperatures. The results at room temperature clearly indicate that the exciton spin concept is not appropriate and should be analyzed by the separate-particle spin concept. Which concept should be applied depends on the relative importance of the spin exchange interaction to the other spin-flip mechanisms.
  • RM Koehl, S Adachi, KA Nelson
    ULTRAFAST PHENOMENA XI 63 136 - 138 1998年 [査読有り][通常論文]
     
    Anharmonic lattice dynamics are investigated with a heterodyne bispectral 2D Raman technique.
  • Y Takagi, S Adachi
    JOURNAL OF LUMINESCENCE 72-4 546 - 547 1997年06月 [査読有り][通常論文]
     
    Transient absorption measurement on HDITCI (hexadibenzocyanine-3) dissolved into ethanol was performed by using a dual-wavelength optical sampling method. From time profile data and time-resolved spectra four successive decays ranging from subpicosecond to nanosecond have been found and assigned to intramolecular vibrational diffusion (0.5 ps), solvation relaxation (5 ps), rotational relaxation (160 ps), and radiative decay (0.5 ns).
  • S. Adachi, T. Miyashita, S. Takeyama, Y. Takagi, A. Tackeuchi
    Journal of Luminescence 72-74 307 - 308 1997年 [査読無し][通常論文]
     
    We have investigated the temperature dependence of the exciton spin relaxation between 10 and 300 K in undoped GaAs quantum wells by using the nonlinear transmission pump-probe and the four-wave-mixing techniques. The electron spin relaxation rate above 40 K is found to be proportional to the product of the temperature and the momentum relaxation time, which indicates that the D'yakonov-Perel' interaction governs the spin-flip dynamics. The temperature independence below 30 K is considered to be due to the band-mixing effect that determines the hole spin relaxation, and the spin exchange is effective to the exciton spin relaxation in these temperatures.
  • S Adachi, T Miyashita, S Takeyama, Y Takagi, A Tackeuchi, M Nakayama
    PHYSICAL REVIEW B 55 3 1654 - 1660 1997年01月 [査読有り][通常論文]
     
    We study the induced absorption due to biexciton formation in absorption bleaching pump-probe signals and the quantum beats between exciton and biexciton in the four-wave-mixing signals. The origin is confirmed by the polarization dependence of the signals in both experiments. The definite discrimination between exciton-biexciton quantum beats and the others by the polarization choices is demonstrated clearly. We also show the well-width dependence of the biexciton binding energy that is determined by the period of the quantum beats in the range of well width 45-150 Angstrom of GaAs/AlxGa1-xAs (x=0.3-1.0) multiple quantum wells.
  • S. Adachi, T. Miyashita, S. Takeyama, Y. Takagi, A. Tackeuchi
    Physical Review B - Condensed Matter and Materials Physics 55 3 1654 - 1660 1997年 [査読有り][通常論文]
     
    We study the induced absorption due to biexciton formation in absorption bleaching pump-probe signals and the quantum beats between exciton and biexciton in the four-wave-mixing signals. The origin is confirmed by the polarization dependence of the signals in both experiments. The definite discrimination between exciton-biexciton quantum beats and the others by the polarization choices is demonstrated clearly. We also show the well-width dependence of the biexciton binding energy that is determined by the period of the quantum beats in the range of well width 45-150 Å of GaAs/(Formula presented)(Formula presented)As (x=0.3-1.0) multiple quantum wells. © 1997 The American Physical Society.
  • S Adachi, S Takeyama, Y Takagi, A Tackeuchi, S Muto
    APPLIED PHYSICS LETTERS 68 7 964 - 966 1996年02月 [査読有り][通常論文]
     
    Spin dynamics in GaAs/AlGaAs multiple quantum wells at room temperature are studied in subpicosecond to nanosecond time region by using the optical sampling nondegenerate pump-probe technique. Polarization-dependent absorption signals resonant to the light-hole (lh) exciton revealed the subpicosecond spin relaxation time which was several tens of times shorter than that of the heavy-hole (hh) exciton. Resonant pumping to lh and probing at hh exhibited no spin dependence within the time resolution, showing the spin memory being washed out completely during the energy relaxation from lh to hh. (C) 1996 American Institute of Physics.
  • S Adachi, S Takeyama, Y Takagi, A Tackeuchi, S Muto
    PROGRESS IN CRYSTAL GROWTH AND CHARACTERIZATION OF MATERIALS 33 1-3 117 - 120 1996年 [査読有り][通常論文]
  • S TAKEYAMA, G GRABECKI, S ADACHI, Y TAKAGI, T WOJTOWICZ, G KARCZEWSKI, J KOSSUT
    ACTA PHYSICA POLONICA A 88 5 945 - 948 1995年11月 [査読有り][通常論文]
     
    Four-single quantum wells composed of the ternary non-magnetic compounds Cd(0.93)Zn(0.0)7Te (well width = 13, 19, 40, 90 Angstrom), separated by the quaternary magnetic-compound Cd0.48Zn0.04Mn0.48Te on (100)GaAs substrate were grown by MBE, and exhibited clear and distinctive photoluminescence lines corresponding to each quantum well. Double luminescence peaks with closely spaced within one well were observed from 90 Angstrom and 40 Angstrom quantum wells. Temperature and magnetic-field study revealed characteristic luminescence features associated with a bound exciton near the interface rather than with one monolayer fluctuation.
  • G GRABECKI, S TAKEYAMA, S ADACHI, Y TAKAGI, T DIETL, E KAMINSKA, A PIOTROWSKA, E PAPIS, N FRANK, G BAUER
    ACTA PHYSICA POLONICA A 88 4 727 - 730 1995年10月 [査読有り][通常論文]
     
    Precise magnetoresistance measurements on microstructures of photolithographically patterned PbSe epilayers have been performed in the magnetic field range up to 17 T. Unusually large, reproducible magnetoconductance fluctuations have been observed. The fluctuation amplitude decreases exponentially with the magnetic field. A correlation magnetic field of the fluctuations corresponds to the Aharonov-Bohm effect which involves electron trajectories much smaller than the electron mean free path. This points strongly to the ballistic, not diffusive, origin of the observed phenomenon.
  • G GRABECKI, S TAKEYAMA, S ADACHI, Y TAKAGI, T DIETL, E KAMINSKA, A PIOTROWSKA, E PAPIS, N FRANK, G BAUER
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS 34 8B 4433 - 4435 1995年08月 [査読無し][通常論文]
     
    Precise magnetoresistance measurements on microstructures of photolithographically patterned PbSe epilayers have been performed in the magnetic field range up to 17 T. Unusual, reproducible magnetoconductance fluctuations have been observed. The fluctuation amplitude is about one order of magnitude greater than that predicted for universal conductance fluctuations. Moreover, the fluctuation frequency spectra correspond to the Aharonov-Bohm effect on electron trajectories up to 50 times smaller than the electron mean free path. This strongly points to the ballistic, not diffusive, origin of the observed phenomenon.
  • S. Takeyama, S. Adachi, Y. Takagi, V. F. Aguekian
    Physical Review B 52 3 1444 - 1447 1995年07月15日 [査読有り]
  • Satoru Adachi, Shojiro Takeyama, Yoshihiro Takagi
    Optics Communications 117 1-2 71 - 77 1995年05月 [査読有り]
  • S. Takeyama, S. Adachi, Y. Takagi, V. F. Aguekian
    Physical Review B 51 8 4858 - 4864 1995年02月15日 [査読有り][通常論文]
  • Y.-W. Chen, C. Yamanaka, H. Niki, S. Adachi, Y. Izawa, S. Nakai
    Journal of the Optical Society of America B 11 9 1585 - 1585 1994年09月01日 [査読有り]
  • S. Adachi, S. Takeyama, Y. Takagi, J.J. Dubowski, E. Deleporte
    Superlattices and Microstructures 16 1 1 - 4 1994年07月 [査読有り]
  • G GRABECKI, S TAKEYAMA, S ADACHI, Y TAKAGI, T WOJTOWICZ, G KARCZEWSKI, J KOSSUT
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 34 59 - 61 1994年 [査読有り][通常論文]
     
    Exciton photoluminescence has been measured in CdZnTe nonmagnetic single quantum wells surrounded by the magnetic CdZnMnTe barriers. Detailed analysis of the both temperature and magnetic field behaviors of the exciton PL lines points to the conclusion that the contribution from the magnetic polaron and/or magnetization fluctuations to the exciton localization energy is rather small and does not exceed 2 meV even at pumping He temperatures, in the quantum wells as narrow as 1.3 nm.
  • Y. Takagi, S. Adachi, S. Takeyama, A. Tackeuchi, S. Muto, J.J. Dubowski
    Journal of Luminescence 58 1-6 202 - 205 1994年01月 [査読有り]
  • V.F. Aguekian, S. Takeyama, S. Adachi, Y. Takagi, N. Miura
    Solid State Communications 86 3 205 - 208 1993年04月 [査読有り]
  • S TAKEYAMA, S ADACHI, Y TAKAGI, VF AGUEKIAN
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 32 425 - 427 1993年 [査読有り][通常論文]
     
    The photoluminescence in CdMnTe (with x = 0.15 and 0.35) was carefully studied and clear evidence for the exciton localization due to magnetic polaron (EMP) formation was presented. It was revealed that the EMP localization induced striking features on the luminescence lines; peak positions, FWHM and intensities. The heavy hole and light hole exciton magnetic polaron stability under the magnetic field was demonstrated distinctly by the polarization measurements.
  • S. Takeyama, S. Adachi, Y. Takagi, N. Miura, V.F. Aguekian
    Journal of Crystal Growth 117 1-4 1081 - 1081 1992年02月 [査読有り]
  • Adachi Satoru, Niki Hideaki, Izawa Yasukazu, Nakai Sadao, Yamanaka Chiyoe
    Japanese Journal of Applied Physics 30 Part 1, No. 10 2515 - 2518 社団法人応用物理学会 1991年10月15日 [査読有り]
     
    Adiabatic inversion processes are discussed for a two-level system. It was found that the required conditions for stable inversion are $\varOmega^{2}/|\mathrm{d}\varDelta/\mathrm{d}t|{\geq}0.5$, $\varDelta_{\text{s } }\tau{\geq}3$ for Gaussian pulse and $\varDelta_{\text{s } }$/$\varOmega$${\geq}11$ for square pulse, where $\varOmega$, $\varDelta$, $\varDelta_{\text{s } }$ and $\tau$ represent Rabi frequency, detuning, frequency-sweep width and optical pulse width, respectively. It was also shown that for Gaussian pulse, adiabatic conditions of $\varDelta_{\text{s } }$/$\varOmega$ and $\varOmega^{2}/|\mathrm{d}\varDelta/\mathrm{d}t|$ are related to each other, while for square pulse, both conditions are determined independently.
  • Satoru Adachi, Hideaki Niki, Yasukazu Izawa, Sadao Nakai, Chiyoe Yamanaka
    Optics Communications 81 6 364 - 368 1991年03月 [査読有り]
  • Adachi Satoru, Niki Hideaki, Izawa Yasukazu, Nakai Sadao, Yamanaka Chiyoe
    Jpn J Appl Phys 29 Part 2, No. 5 L833 - L836 社団法人応用物理学会 1990年05月20日 [査読有り]
     
    Dipole matrix elements were measured for two transitions of the gadolinium atom by detecting the laser-induced fluorescence as a function of laser intensity using Rabi flopping. Those values are $2.7\times 10^{-19}$ and $3.0\times 10^{-19}$ esu$\cdot$cm for 9D2-9F2(0-17381 cm-1) and 9D5-9D4(999–17931 cm-1), respectively. Optical Bloch equations for two-level atoms were calculated for each pair of magnetic sublevels, where the effects of inhomogeneous broadening and laser intensity fluctuation were included. Experimental results were well described by this model. This method is very useful for determining a dipole matrix element which is one of the basic parameters for laser isotope separation.
  • Development of a Single-Mode Dye Laser Pumped by a Copper Vapor Laser
    荒井康, 仁木秀明, 足立智, 竹田哲也, 山中龍彦, 山中千代衛
    Technology Reports of the Osaka University 36 1860 361 - 367 1986年 [査読無し][通常論文]

書籍

  • コヒーレントフォノン計測
    足立 智 (担当:共著範囲:レーザーハンドブック 26章レーザーによる科学計測 第4節)
    2004年

講演・口頭発表等

  • 量子情報プラットフォームとしてのEr添加固体材料の開発  [招待講演]
    俵 毅彦, 平石 真也, 稲葉 智宏, 徐 学俊, 太田 竜一, 足立 智, 尾身 博雄
    第82回応用物理学会秋季学術講演会 2021年09月 口頭発表(招待・特別)
  • Evaluation of homogeneous linewidth of 167Er3+:Y2SiO5 in frequency domain measurement using laser stabilization with optical frequency comb  [通常講演]
    S. Yasui, M. Hiraishi, A. Ishizawa, H. Omi, R. Kaji, S. Adachi, T. Tawara
    The 2021 International Conference on Solid State Devices and Materials (SSDM2021) 2021年09月 口頭発表(一般)
  • Double nuclear spin switching in single self-assembled quantum dots  [通常講演]
    S. Yamamoto, R. Kaji, H. Sasakura, S. Adachi
    The 2020 International Conference on Solid State Devices and Materials (SSDM2020) 2020年09月 口頭発表(一般)
  • Photon statics in a single quantum dot under bistable state of nuclear spin polarization  [通常講演]
    R. Kaji, R. Matsusaki, K. Omiya, S. Kamono, H. Sasakura, S. Adachi
    International Conference on Optics of Excitons in Confined Systems 2019年09月 口頭発表(一般)
  • Large in-plane nuclear field formation in single quantum dots: Influence of a longitudinal field and role of nuclear quadrupolar interaction  [通常講演]
    S. Yamamoto, T. Arakawa, R. Matsusaki, R. Kaji, S. Adachi
    International Conference on Optics of Excitons in Confined Systems 2019年09月 ポスター発表
  • ナノ構造半導体での面内核磁場形成  [招待講演]
    足立 智, 山本 壮太, 荒川 拓也, 鍜治 怜奈
    日本物理学会2019年秋季大会 2019年09月 口頭発表(招待・特別)
  • Modulation of nuclear quadrupole effect by a longitudinal magnetic field in transverse nuclear field formation  [通常講演]
    S. Yamamoto, T. Arakawa, R. Matsusaki, R. Kaji, S. Adachi
    The 46th International Symposium on Compound Semiconductors 2019年05月 口頭発表(一般)
  • Evaluation of Rabi frequency and coherence time in the hyperfine structure of 167Er3+ in Y2SiO5 through coherent transients  [通常講演]
    M. Hiraishi, M. IJspeert, T. Tawara, S. Adachi, H. Omi, H. Gotoh
    The 46th International Symposium on Compound Semiconductors 2019年05月 口頭発表(一般)
  • Nuclear spin switching in a single quantum dot  [招待講演]
    S. Adachi
    The 3rd Japan-Taiwan International Engineering Forum 2019年02月 口頭発表(一般)
  • Studies on anomalous Hanle effect observed in single self-assembled quantum dots  [通常講演]
    R. Kaji, S. Yamamoto, R. Matsusaki, S Adachi
    The 50th International Conference on Solid State Devices and Materials: SSDM2018 2018年09月 口頭発表(一般)
  • A novel method for direct evaluation of nuclear spin fluctuation by using nuclear spin switch in quantum nanostructures  [通常講演]
    R. Kaji, R. Matsusaki, S. Yamamoto, S Adachi
    The 50th International Conference on Solid State Devices and Materials: SSDM2018 2018年09月 ポスター発表
  • Anomalous Hanle curves induced by in-plane nuclear field in single self-assembled InAlAs and InAs nanostructures  [通常講演]
    S. Yamamoto, R. Matsusaki, R. Kaji, S Adachi
    The 12th International Conference on Excitonic and Photonic Processes in Condensed Matter and Nano Materials: EXCON2018 2018年07月 ポスター発表
  • Formation of nuclear field orthogonal to electron spin and nuclear quadrupole effects in self-assembled single quantum dots  [通常講演]
    S. Yamamoto, R. Matsusaki, R. Kaji, S Adachi
    50 years of optical orientation in semiconductors: From the original discovery to new horizons 2018年06月 ポスター発表
  • State preparation and lifetime measurements through spectral hole burning in 167Er3+:Y2SiO5  [通常講演]
    M. IJspeert, M. Hiraishi, T. Tawara, K. Shimizu, H. Omi, S. Adachi, H. Gotoh
    International School and Symposium on Nanoscale Transport and phoTonics (ISNTT2017) 2017年11月 ポスター発表
  • n-plane nuclear field formation in individual InAlAs quantum dots: role of nuclear quadrupole effects  [通常講演]
    S. Yamamoto, R. Matsusaki, R. Kaji, S Adachi
    International School and Symposium on Nanoscale Transport and phoTonics (ISNTT2017) 2017年11月 ポスター発表
  • Evaluations of the electron g-factor anisotropy and fuctuationof the Overhauser field in single quantum dots  [通常講演]
    R. Matsusaki, S. Yamamoto, R. Kaji, S Adachi
    International School and Symposium on Nanoscale Transport and phoTonics (ISNTT2017) 2017年11月 ポスター発表
  • Formation of transverse nuclear field in single self-assembled quantum dots: role of quadrupolar splitting  [招待講演]
    S Adachi
    International Workshop on NanoScience and NanoOptics 2017年11月 口頭発表(招待・特別)
  • Population trapping through spectral hole burning in 167Er3+:Y2SiO5  [通常講演]
    M. IJspeert, G. Mariani, T. Tawara, K. Shimizu, H. Omi, S. Adachi, H. Gotoh
    International Conference on Solid-State Devices and Materials (SSDM2017) 2017年09月 口頭発表(一般)
  • Λ-system Initialisation through Spectral Hole Burning in 167Er3+:Y2SiO5  [通常講演]
    M. IJspeert, G. Mariani, T. Tawara, K. Shimizu, H. Omi, S. Adachi, H. Gotoh
    International Symposium on Hybrid Quantum Systems 2017 (HSQ2017) 2017年09月 口頭発表(一般)
  • Quadrupolar effect for nuclear spin depolarization in a single InAlAs quantum dot  [通常講演]
    R. Kaji, R. Matsusaki, S. Yamamoto, H. Sasakura, S. Adachi
    International Conference on Optics of Excitons in Confined Systems (OECS2017) 2017年09月 ポスター発表
  • Formation mechanism of in-plane Overhauser field in single self-assembled InAlAs quantum dots  [通常講演]
    S. Yamamoto, R. Matsusaki, R. Kaji, S Adachi
    International Conference on Optics of Excitons in Confined Systems (OECS2017) 2017年09月 ポスター発表
  • Quadrupolar effect in zero-field dynamic nuclear spin polarization of a single self-assembled InAlAs quantum dot  [通常講演]
    R. Matsusaki, S. Yamamoto, R. Kaji, S. Adachi
    The 9th International Conference on Spintronics and Quantum Information Technology 2017年06月 ポスター発表
  • Spectral Hole Narrowing in Er3+ 4f Transitions by Isotope Separation  [通常講演]
    T. Tawara, G. Mariani, K. Shimizu, H. Omi, S. Adachi, H. Gotoh
    Conference on Lasers and Electro-Optics (CLEO2017) 2017年05月 ポスター発表
  • Investigation of Spin Dynamics Based on Initial Phase Shift Analysis of Kerr Rotation in a CdTe Single Quantum Well  [通常講演]
    L.-P. Yan, R. Kaji, S. Adachi
    The 43rd International Symposium on Compound Semiconductors (ISCS) 2016年06月 ポスター発表
  • Hole g-Factor Anisotropies in Individual InAs Quantum Rings  [通常講演]
    R. Kaji, T. Tominaga, Y.-N. Wu, M.-F. Wu, S.-J. Cheng, S. Adachi
    The 43rd International Symposium on Compound Semiconductors (ISCS) 2016年06月 口頭発表(一般)
  • Photonic crystal membrane with single crystalline rare-earth oxide using selective area growth by MBE  [通常講演]
    T. Tawara, H. Omi, T. McManus, A. Llenas, E. Kuramochi, S. Adachi, H. Gotoh
    The 43rd International Symposium on Compound Semiconductors (ISCS) 2016年06月 口頭発表(一般)
  • Control of energy transfer up-conversion by photonic band gap in Er2O3 epitaxial layers  [通常講演]
    T. Tawara, A. Llenas, T. McManus, H. Omi, E. Kuramochi, S. Adachi, H. Gotoh
    International Symposium on Nanoscale Transport and Technology (ISNTT2015) 2015年11月 ポスター発表
  • Anisotropy of electron and hole in-plane g-factors in single InAs/GaAs quantum rings  [通常講演]
    T. Tominaga, R. Kaji, Y.-N. Wu, S.-J. Cheng, S Adachi
    17th International Conference on Modulated Semiconductor Structures (MSS17) 2015年07月 ポスター発表
  • Anisotropy of electron and hole g-factors in individual InAs quantum rings  [招待講演]
    R. Kaji, S. Adachi
    Japan, Vietnam, Bulgaria and Taiwan Joint Workshop 2015年07月 口頭発表(招待・特別)
  • Inter- and intra-site energy transfers in (Er, Sc)2O3 thin films grown on Si(111)  [通常講演]
    Y. Kawakami, T. Tawara, H. Omi, R. Kaji, S. Adachi
    19th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON 19) 2015年07月 ポスター発表
  • Electron and hole in-plane g-factors in single InAs quantum rings  [通常講演]
    R. Kaji, T. Tominaga, Y.-N. Wu, S.-J. Cheng, S. Adachi
    19th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON 19) 2015年07月 口頭発表(一般)
  • Formation dynamics and initial phase shift of resident electron spin polarization observed by time-resolved Kerr rotation spectroscopy  [通常講演]
    L.-P.Yan, R. Kaji, S. Adachi
    17th International Conference on Modulated Semiconductor Structures (MSS17) 2015年06月 ポスター発表
  • Visible up-conversion luminescence in (ErSc)2O3 epitaxial thin films and its suppression by photonic band-gap  [通常講演]
    T. Tawara, T. McManus, Y. Kawakami, H. Omi, A. Najar, R. Kaji, S. Adachi, H. Gotoh
    onference on Lasers and Electro-Optics (CLEO:2015) 2015年05月 口頭発表(一般)
  • Electron and hole spin dephasing induced by nuclear field fluctuation in semiconductor quantum dots  [招待講演]
    R. Kaji, S. Adachi
    International Symposium on Recent Progress of Photonic Devices and Materials 2014年11月 口頭発表(招待・特別)
  • Effective nuclear field measurement in a single quantum well via time-resolved Kerr rotation technique  [通常講演]
    L.-P. Yan, R. Kaji, S. Adachi
    International Conference on Materials Science and Engineering Technology (MSET 2014) 2014年06月 口頭発表(一般)
  • Optical transition between Stark levels in (ErSc)2O3 epitaxitial films  [通常講演]
    T. Tawara, H. Omi, A. Najar, R. Kaji, S. Adachi, H. Gotoh
    Conference on Lasers and Electro-Optics (CLEO:2014) 2014年06月 ポスター発表
  • Molecular beam epitaxy of (ErxSc1-x)2O3 in Si(111)  [通常講演]
    H. Omi, T. Tawara, T. Hozumi, R. Kaji, S. Adachi, H. Gotoh, T. Sogawa
    2nd International Conference on Photonics, Optics and Laser Technology (PHOTOPTICS 2014) 2014年01月 ポスター発表
  • Resident electrons spin formation and spin dephasing in a single CdTe quantum well  [通常講演]
    L.-P. Yan, W.-T.Hsu, S. Adachi
    International Conference on Solid State Devices and Materials (SSDM13) 2013年09月 ポスター発表
  • MBE growth and optical properties of rear earth oxides on Si(111)  [通常講演]
    H.Omi, T. Tawara, T. Hozumi, R. Kaji, T. Adachi, H. Gotoh, T. Sougawa
    2013 JSAP-MRS Joint Symposia 2013年09月 口頭発表(一般)
  • Magneto-optical properties of Er2O3 epilayers on Si(111)  [通常講演]
    T. Hozumi, R. Kaji, S. Adachi, T. Tawara, H. Omi
    2013 JSAP-MRS Joint Symposia 2013年09月 ポスター発表
  • Energy transfer in epitaxial Er2O3 thin films grown on Si(111) substrates  [通常講演]
    T. Tawara, T. Hozumi, H. Omi, R. Kaji, S. Adachi, H. Gotoh, T. Sogawa
    IEEE Photonics Conference 2013 2013年09月 口頭発表(一般)
  • Electron and hole g-factor measurements via optically-induced nuclear spin polarizations in single InAs/GaAs quantum rings  [通常講演]
    R. Kaji, T. Hozumi, S. Ohno, S. Adachi
    13th International Conference on Optics of Excitons in Confined System: OECS13 2013年08月 口頭発表(一般)
  • Impact of band mixing to heavy hole spin dephasing induced by nuclear field fluctuation  [通常講演]
    R. Kaji, S. Ohno, T. Hozumi, S. Adachi
    18th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures: EDISON18 2013年07月 口頭発表(一般)
  • Arbitrary qubit rotation by double STIRAP in Er2O3 thin film  [通常講演]
    Y. Kawakami, T. Hozumi, R. Kaji, S. Adachi, T. Tawara, H. Omi
    18th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures: EDISON18 2013年07月 口頭発表(一般)
  • Exciton-exciton interactions in tensile-strained GaN  [通常講演]
    Y. Toda, K. Shigematsu, A. Hasegawa, S. Adachi
    International Workshop on NItride Semiconductors:IWN2012 2012年10月 口頭発表(一般)
  • Size distribution and scaling function of InAlAs/AlGaAs quantum dots grown on GaAs by molecular beam epitaxy  [通常講演]
    X. M. Lu, M. Koyama, Y. Izumi, S. Adachi, S. Muto
    7th International Conference on MBE:MBE2012 2012年09月 ポスター発表
  • Spin interactions of electron and nuclei in individual quantum dots  [招待講演]
    S. Adachi
    Workshop on“Fabrication, Spectroscopy and Modeling of Semiconductor Quantum Dots 2012年03月 口頭発表(招待・特別)

その他活動・業績

特許

  • 特開USSN 60/092,429:Polariton Wave Imaging  
    足立 智  Keith A. Nelson, Satoru Adachi, Richard M. Koehl
  • 位相干渉計測手法及び位相干渉計測装置
    2006-128277
  • 「光計測評価方法および光計測評価装置」(世界知的所有権)
    PCT/JP2005/020410
  • 光計測評価方法及び光計測評価装置
    2004-331123

共同研究・競争的資金等の研究課題

  • 日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2021年04月 -2024年03月 
    代表者 : 足立 智, 鍜治 怜奈, 笹倉 弘理
  • 単一光子エンタングルメントを介したスピン間制御
    日本学術振興会:科学研究費助成事業 基盤研究(B)
    研究期間 : 2020年04月 -2024年03月 
    代表者 : 笹倉 弘理, 足立 智, 小田島 聡, 鍜治 怜奈, 熊野 英和
  • ノイズ分光による3次元スピン情報マッピング
    日本学術振興会:科学研究費助成事業 挑戦的研究(萌芽)
    研究期間 : 2021年07月 -2023年03月 
    代表者 : 足立 智
  • スピンノイズ・核磁気共鳴法で観る電子・核スピン結合系のミクロな揺らぎ
    日本学術振興会:科学研究費助成事業 基盤研究(C)
    研究期間 : 2020年04月 -2023年03月 
    代表者 : 鍜治 怜奈, 足立 智
  • 日本学術振興会:科学研究費補助金 基盤研究(B)
    研究期間 : 2019年04月 -2022年03月 
    代表者 : 俵 毅彦
  • 半導体ナノ構造での自発分極を利用した核スピン完全偏極
    日本学術振興会:挑戦的研究(萌芽)
    研究期間 : 2017年04月 -2019年03月 
    代表者 : 足立 智
  • 光学的核スピンエンジニアリングと局在スピン操作
    日本学術振興会:基盤研究(A)
    研究期間 : 2013年04月 -2017年03月 
    代表者 : 足立 智
  • 酸化エルビウム結晶におけるポピュレーション操作と量子メモリへの応用
    日本学術振興会:科学研究補助金 基盤研究(B)
    研究期間 : 2012年04月 -2015年03月 
    代表者 : 俵 毅彦
  • スピンコヒーレンスの新規検出法の実証と電子スピン高速制御への展開
    日本学術振興会:科学研究費補助金 挑戦的萌芽研究
    研究期間 : 2012年04月 -2014年03月 
    代表者 : 足立 智
  • 半導体核スピンの全光ナノプローブ技術と実時間イメージング技術の開発
    日本学術振興会:科学研究費補助金基盤研究(B)(一般)
    研究期間 : 2010年04月 -2013年03月 
    代表者 : 足立 智
  • 量子ドットにおける核スピンの双安定性を利用した量子ビット変換
    財団法人テレコム先端技術研究支援センター:SCAT研究費助成
    研究期間 : 2008年04月 -2011年03月 
    代表者 : 足立 智
  • テラヘルツ光による単一量子ドットの電子スピン転送操作
    日本学術振興会:科学研究費補助金 基盤研究(B)一般
    研究期間 : 2005年 -2008年03月 
    代表者 : 足立 智
  • ワイドギャップ半導体結晶における歪の高感度空間マッピング
    日本学術振興会:科学研究費補助金 萌芽研究
    研究期間 : 2006年04月 -2007年03月 
    代表者 : 足立 智
  • 量子ドットを使った光誘起ナノマグネットの形成とその光制御
    日本学術振興会:科学研究費補助金 萌芽研究
    研究期間 : 2005年04月 -2006年03月 
    代表者 : 足立 智
  • 半導体量子ドットの電子スピンコヒーレンス制御と量子コンピューティングへの応用
    東電記念科学研究所:研究助成
    研究期間 : 2001年04月 -2004年03月 
    代表者 : 足立 智
  • Hyperfine interaction in semiconductor quantum dots
    研究期間 : 2004年
  • フォノンイメージングによる非線形光学材料評価システムの開発
    日本学術振興会:科学研究費補助金 基盤研究(B)(2)
    研究期間 : 2001年04月 -2003年03月 
    代表者 : 足立 智
  • 量子構造半導体でのスピン拡散のイメージングと拡散機構の解明
    財団法人テレコム先端技術研究支援センター:SCAT研究費助成
    研究期間 : 2001年04月 -2003年03月 
    代表者 : 足立 智
  • Control of spin coherence in nanostructures
    JST Basic Research Programs (Core Research for Evolutional Science and Technology :CREST)
    研究期間 : 2003年
  • フォノンイメージングによる誘電体結晶評価システムの構築
    日本板硝子材料工学助成会:研究助成
    研究期間 : 2001年04月 -2002年03月 
    代表者 : 足立 智
  • 整形パルスによる誘電体結晶中での伝播波束の制御とイメージング
    カシオ科学振興財団:研究助成
    研究期間 : 2000年04月 -2002年03月 
    代表者 : 足立 智
  • 量子構造半導体における励起子スピン拡散及び緩和過程のイメージング分光
    日本学術振興会:科学研究費補助金 基盤研究(C)(2)
    研究期間 : 2000年04月 -2002年03月 
    代表者 : 足立 智
  • 高時間分解反射型空間イメージング法の開発と量子構造半導体における励起子スピン拡散への応用
    村田学術振興財団:研究助成
    研究期間 : 2000年04月 -2001年03月 
    代表者 : 足立 智
  • 高強度レーザーのパルス整形技術の開発と応用
    大阪大学レーザー核融合研究センター:共同研究
    研究期間 : 2000年04月 -2001年03月 
    代表者 : 足立 智
  • 熱非平衡状態下でのレーザー誘起格子振動を利用した不純物ドーピングに関する研究
    生産技術研究奨励会:旅費支援
    研究期間 : 1999年04月 -2000年03月 
    代表者 : 足立 智
  • 固体中を伝播するフォノンポラリトンの2次元イメージングに関する研究
    実吉奨学会:研究助成
    研究期間 : 1998年09月 -1999年09月 
    代表者 : 足立 智

教育活動情報

主要な担当授業

  • レーザー分光特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : 固体光物性, スピン,コヒーレンス,光との相互作用
  • 応用物理学特別講義一
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : 量子光学と量子力学,量子情報処理,単一光子,もつれ合い光子対,ベル測定
  • レーザー分光特論
    開講年度 : 2021年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : 固体光物性, スピン,コヒーレンス,光との相互作用
  • 電子工学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : 線形回路,過渡応答,周波数解析,半導体,ダイオード,トランジスタ,サンプリング定理,離散時間フーリエ変換,量子化
  • 応用物理学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : ナノテク・ナノサイエンス、光科学、量子力学、複雑ネットワーク
  • 応用物理学
    開講年度 : 2021年
    課程区分 : 学士課程
    開講学部 : 工学部
    キーワード : ナノテクノロジー、光科学、複雑ネットワーク、電子顕微鏡、太陽系外惑星


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