研究者詳細 - 藤原　正澄

論文 - 藤原　正澄

分割表示 109 件中 61 - 80 件目／全件表示 >>

Phase shift spectra of a fiber-microsphere system at the single photon level 査読

Akira Tanaka, Takeshi Asai, Kiyota Toubaru, Hideaki Takashima, Masazumi Fujiwara, Ryo Okamoto, Shigeki Takeuchi

OPTICS EXPRESS 19 ( 3 ) 2278 - 2285 2011年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：OPTICAL SOC AMER

We succeeded in measuring phase shift spectra of a microsphere cavity coupled with a tapered fiber using a weak coherent probe light at the single photon level. We utilized a tapered fiber with almost no depolarization and constructed a very stable phase shift measurement scheme based on polarization analysis using photon counting. Using a very weak probe light ((n) over bar = 0.41), we succeeded in observing the transition in the phase shift spectrum between undercoupling and overcoupling (at gap distances of 500 and 100 nm, respectively). We also used quantum state tomography to obtain a 'purity spectrum'. Even in the overcoupling regime, the average purity was 0.982 +/- 0.024 (minimum purity: 0.892), suggesting that the coherence of the fiber-microsphere system was well preserved. Based on these results, we believe this system is applicable to quantum phase gates using single light emitters such as diamond nitrogen vacancy centers. (C) 2011 Optical Society of America

DOI： 10.1364/OE.19.002278

DOI： 10.1364/oe.19.002278

Phase shift spectra of a fiber-microsphere system at the single photon level 査読

Akira Tanaka, Takeshi Asai, Kiyota Toubaru, Hideaki Takashima, Masazumi Fujiwara, Ryo Okamoto, Shigeki Takeuchi

OPTICS EXPRESS 19 ( 3 ) 2278 - 2285 2011年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：OPTICAL SOC AMER

We succeeded in measuring phase shift spectra of a microsphere cavity coupled with a tapered fiber using a weak coherent probe light at the single photon level. We utilized a tapered fiber with almost no depolarization and constructed a very stable phase shift measurement scheme based on polarization analysis using photon counting. Using a very weak probe light ((n) over bar = 0.41), we succeeded in observing the transition in the phase shift spectrum between undercoupling and overcoupling (at gap distances of 500 and 100 nm, respectively). We also used quantum state tomography to obtain a 'purity spectrum'. Even in the overcoupling regime, the average purity was 0.982 +/- 0.024 (minimum purity: 0.892), suggesting that the coherence of the fiber-microsphere system was well preserved. Based on these results, we believe this system is applicable to quantum phase gates using single light emitters such as diamond nitrogen vacancy centers. (C) 2011 Optical Society of America

DOI： 10.1364/OE.19.002278

Optical quantum circuit combining tailored optical nonlinearities 査読

Shigeki Takeuchi, Ryo Okamoto, Masazumi Fujiwara, Hong-Quan Zhao, Holger F. Hofmann, Jeremy L. O'Brien

2011 Conference on Lasers and Electro-Optics Europe and 12th European Quantum Electronics Conference, CLEO EUROPE/EQEC 2011 2011年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

We report our recent experimental demonstration of a KLM CNOT gate[1], a photonic quantum circuit to combine two efficient artificial nonlinear elements. This experimental demonstration[2] confirms the first step in the KLM recipe for all-optical quantum computation, and should be useful for on-demand entanglement generation and purification. We will also report our activities toward the realization of nonlinear sign shift gate using diamond nano-crystals coupled to a microsphere cavity[3]. © 2011 IEEE.

DOI： 10.1109/CLEOE.2011.5943453

Polarization-purity spectra of a tapered-fiber-coupled microsphere cavity system at cryogenic temperatures 査読

Masazumi Fujiwara, Akira Tanakaa, Kiyota Toubarua, Hong-Quan Zhao, Hideaki Takashima, Shigeki Takeuchi

LASER RESONATORS AND BEAM CONTROL XIII 7913 2011年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：SPIE-INT SOC OPTICAL ENGINEERING

An ultrahigh-Q optical microcavity coupled with a tapered fiber is an ideal system for the cavity quantum electrodynamics (CQED). In particular realizing this system at cryogenic temperature is vitally important and has been recently explored for various CQED applications including solid-state atom-photon strong coupling, vibrational mode cooling, and photonic quantum gates. These cryogenic fiber-coupled microcavity systems, however, suffer from mechanical vibrations due to cooling systems and distortions caused by large temperature change. These factors may cause the degradation in polarization of probe light field in the system. Here we report the analysis of the polarization state in a tapered-fiber-coupled microsphere cavity at cryogenic temperatures. By scanning the wavelength of the probe light at around 637 nm, which can be used for the diamond nitrogen vacancy centers, the spectral analysis of the polarization state was performed at 8-30 K. We have found that the degree of polarization (DOP, classical analogue of purity) at cryogenic temperatures does not show significant change compared to that measured at room temperature. This fact indicates that the system can conserve the polarization at low temperature to the extent comparable to that at room temperature, which is enough for the evaluation of the quantum phase gate.

DOI： 10.1117/12.874587

Ultrafast relaxation kinetics in β-carotene homologs having different methyl side groupsMulti-Pulse Excitation 査読

Y. Iwabuchi, K. Abe, R. Nakamura, D. Kosumi, M. Fujiwara, R. Fujii, H. Hashimoto, M. Yoshizawa

Carotenoid Science 15 26 - 29 2010年12月

Determination of the d-Tensor Components of a Single Crystal of N-Benzyl-2-methyl-4-nitroaniline (vol 46, pg 1528, 2007) 査読

Masazumi Fujiwara, Minoru Maruyama, Mitsuru Sugisaki, Hironori Takahashi, Shin-ichiro Aoshima, Richard J. Cogdell, Hideki Hashimoto

JAPANESE JOURNAL OF APPLIED PHYSICS 49 ( 11 ) 2010年11月

Erratum: Determination of the d-tensor components of a single crystal of N-benzyl-2-methyl-4-nitroaniline (Japanese Journal of Applied Physics (2007) 46 (1528)) 査読

Masazumi Fujiwara, Minoru Maruyama, Mitsuru Sugisaki, Hironori Takahashi, Shin-Ichiro Aoshima, Richard J. Cogdell, Hideki Hashimoto

Japanese Journal of Applied Physics 49 ( 11 ) 2010年11月

Determination of the d-Tensor Components of a Single Crystal of N-Benzyl-2-methyl-4-nitroaniline (vol 46, pg 1528, 2007) 査読

Masazumi Fujiwara, Minoru Maruyama, Mitsuru Sugisaki, Hironori Takahashi, Shin-ichiro Aoshima, Richard J. Cogdell, Hideki Hashimoto

JAPANESE JOURNAL OF APPLIED PHYSICS 49 ( 11 ) 119201 - 119201-1 2010年11月

Ultrafast relaxation kinetics of the dark S-1 state in all-trans-beta-carotene explored by one- and two-photon pump-probe spectroscopy 査読

Daisuke Kosumi, Kenta Abe, Hiroshi Karasawa, Masazumi Fujiwara, Richard J. Cogdell, Hideki Hashimoto, Masayuki Yoshizawa

CHEMICAL PHYSICS 373 ( 1-2 ) 33 - 37 2010年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Femtosecond one-and two-photon pump-probe dispersive spectroscopic measurements have been applied to the investigation of the vibrational relaxation kinetics of the dark S-1 (2(1)A(g)(-)) state in beta-carotene, combining a higher sensitive detection system with tunable visible and infrared excitation pulses. The two-photon excitation measurements enable the preferential detection of the dark S-1 state. The tunable infrared excitation pulses allowed selective excitation to a different vibrational level of S-1. The S-1 dynamics at early delay times depend strongly on excitation energy. A dependence of the initial S-1 dynamics on excitation energy is discussed in term of the vibrational relaxation of S-1. (C) 2009 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.chemphys.2009.12.013

Ultrafast relaxation kinetics of the dark S-1 state in all-trans-beta-carotene explored by one- and two-photon pump-probe spectroscopy 査読

Daisuke Kosumi, Kenta Abe, Hiroshi Karasawa, Masazumi Fujiwara, Richard J. Cogdell, Hideki Hashimoto, Masayuki Yoshizawa

CHEMICAL PHYSICS 373 ( 1-2 ) 33 - 37 2010年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Femtosecond one-and two-photon pump-probe dispersive spectroscopic measurements have been applied to the investigation of the vibrational relaxation kinetics of the dark S-1 (2(1)A(g)(-)) state in beta-carotene, combining a higher sensitive detection system with tunable visible and infrared excitation pulses. The two-photon excitation measurements enable the preferential detection of the dark S-1 state. The tunable infrared excitation pulses allowed selective excitation to a different vibrational level of S-1. The S-1 dynamics at early delay times depend strongly on excitation energy. A dependence of the initial S-1 dynamics on excitation energy is discussed in term of the vibrational relaxation of S-1. (C) 2009 Elsevier B. V. All rights reserved.

DOI： 10.1016/j.chemphys.2009.12.013

Fiber-microsphere system at cryogenic temperatures toward cavity QED using diamond NV centers 査読

Hideaki Takashima, Takeshi Asai, Kiyota Toubaru, Masazumi Fujiwara, Keiji Sasaki, Shigeki Takeuchi

OPTICS EXPRESS 18 ( 14 ) 15169 - 15173 2010年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：OPTICAL SOC AMER

The coupling of a microsphere resonator to a tapered fiber was demonstrated at cryogenic temperatures (8 - 13 K) and investigated with a probe laser light whose frequency around the zero phonon line of nitrogen vacancy centers in diamond (638 nm). For this purpose, a liquid-helium-flow cryostat with a large sample chamber is developed and a resonance dip with a Q of 2 x 10(6) is observed. The resonance frequency and the coupling condition are found to be stable for a period of one hour. (C) 2010 Optical Society of America

DOI： 10.1364/OE.18.015169

Comparison of transient grating signals from spheroidene in an organic solvent and in pigment-protein complexes from Rhodobacter sphaeroides 2.4.1 査読

Mitsuru Sugisaki, Masazumi Fujiwara, Daisuke Kosumi, Ritsuko Fujii, Mamoru Nango, Richard J. Cogdell, Hideki Hashimoto

PHYSICAL REVIEW B 81 ( 24 ) 2010年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

The concurrent dynamics of the electronic excitation and vibronic oscillations of spheroidene have been investigated by means of the transient grating (TG) spectroscopy. The third-order optical responses of spheroidene in an organic solvent, in the LH2 light-harvesting antenna complexes, and in chromatophores have been compared in order to investigate the influence of the environment surrounding this photosynthetic pigment. Vibronic coherent oscillations with a period of several tens of femtosecond have been clearly observed superimposed on a slowly varying background, which reflects the electronic dynamics. The dynamics of the coherent oscillations have been analyzed by means of the wavelet analysis. Within our experimental accuracy, the decay times of the C=C and C-C stretching modes and C-CH(3) rocking mode of each specimen are very close. The experimental results have also been analyzed using a Brownian oscillator model. For these numerical calculations, the spectral density for the underdamped modes has been determined from the Raman spectrum of spheroidene. It was found that the low-frequency modes that reflect the influence of the protein environment can be approximated by the overdamped Brownian oscillator. The experimentally observed linear absorption spectra as well as the third-order optical responses, i.e., TG curves, are reproduced very well by these calculations. The close agreement between the experiments and calculations indicates that the Feynman-diagrammatic approach can be applied to express not only the internal conversion but also the intermolecular excitation energy-transfer processes. The vibronic decay rates of spheroidene in LH2 complexes and chromatophores are evaluated to be about 20% larger than in the organic solvent.

DOI： 10.1103/PhysRevB.81.245112

Comparison of transient grating signals from spheroidene in an organic solvent and in pigment-protein complexes from Rhodobacter sphaeroides 2.4.1 査読

Mitsuru Sugisaki, Masazumi Fujiwara, Daisuke Kosumi, Ritsuko Fujii, Mamoru Nango, Richard J. Cogdell, Hideki Hashimoto

PHYSICAL REVIEW B 81 ( 24 ) 2010年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

The concurrent dynamics of the electronic excitation and vibronic oscillations of spheroidene have been investigated by means of the transient grating (TG) spectroscopy. The third-order optical responses of spheroidene in an organic solvent, in the LH2 light-harvesting antenna complexes, and in chromatophores have been compared in order to investigate the influence of the environment surrounding this photosynthetic pigment. Vibronic coherent oscillations with a period of several tens of femtosecond have been clearly observed superimposed on a slowly varying background, which reflects the electronic dynamics. The dynamics of the coherent oscillations have been analyzed by means of the wavelet analysis. Within our experimental accuracy, the decay times of the C=C and C-C stretching modes and C-CH(3) rocking mode of each specimen are very close. The experimental results have also been analyzed using a Brownian oscillator model. For these numerical calculations, the spectral density for the underdamped modes has been determined from the Raman spectrum of spheroidene. It was found that the low-frequency modes that reflect the influence of the protein environment can be approximated by the overdamped Brownian oscillator. The experimentally observed linear absorption spectra as well as the third-order optical responses, i.e., TG curves, are reproduced very well by these calculations. The close agreement between the experiments and calculations indicates that the Feynman-diagrammatic approach can be applied to express not only the internal conversion but also the intermolecular excitation energy-transfer processes. The vibronic decay rates of spheroidene in LH2 complexes and chromatophores are evaluated to be about 20% larger than in the organic solvent.

DOI： 10.1103/PhysRevB.81.245112

Highly sensitive femtosecond dispersive spectroscopy: Application to the ultrafast relaxation kinetics in all-trans-β-carotene 査読

D. Kosumi, K. Abe, H. Karasawa, M. Fujiwara, H. Hashimoto, M. Yoshizawa

Carotenoid Science 14 37 - 42 2009年12月

Transient grating spectroscopy in photosynthetic purple bacteria Rhodobacter sphaeroides 2.4.1 査読

Mitsuru Sugisaki, Masazumi Fujiwara, Ritsuko Fujii, Katsunori Nakagawa, Mamoru Nango, Richard J. Cogdell, Hideki Hashimoto

JOURNAL OF LUMINESCENCE 129 ( 12 ) 1908 - 1911 2009年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The vibronic coherence of photosynthetic pigment-protein complexes has been investigated by means of transient grating spectroscopy using sub 20 fs optical pulses. In the present work, we focus our attention on the LH2 antenna complexes from Rhodobacter sphaeroides 2.4.1 because the information about their Structure investigated by the electron and atomic force microscopy is available and the electric levels of pigments are well resolved, resulting in clear absorption spectrum. The vibronic coherent oscillations with a period of a few tens of femtoseconds have been clearly observed We found that the temporal change of the coherent oscillations reflects the vibrational relaxation in the ground state. Calculations based on the Brownian oscillator model were performed Under the impulsive excitation limit. The spectral density has been determined from the Raman measurement of spheroidene. Good agreement between the calculation and the experimental results has been achieved in the linear absorption spectrum and transient grating signal, which strongly Supports the validity of our model. (C) 2009 Elsevier B.V. All rights reserved

DOI： 10.1016/j.jlumin.2009.01.027

Ultrafast optical responses of beta-carotene and lycopene probed by sub-20-fs time-resolved coherent spectroscopy 査読

M. Fujiwara, M. Sugisaki, A. Gall, B. Robert, R. J. Cogdell, H. Hashimoto

JOURNAL OF LUMINESCENCE 129 ( 12 ) 1808 - 1812 2009年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

We investigate how structural distortions in carotenoid cause decoherences of its high-frequency vibrational modes by applying the sub-20-fs time-resolved transient grating spectroscopy to beta-catotene and lycopene. The results indicate that the C = C central stretching mode shows significant loss of coherence under the effects of the steric hindrance between beta-ionone ring and polyene backbone, whereas the other high-frequency modes do not show such dependency on the structural distortions. (C) 2000 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jlumin.2009.04.098

Ultrafast optical responses of beta-carotene and lycopene probed by sub-20-fs time-resolved coherent spectroscopy 査読

M. Fujiwara, M. Sugisaki, A. Gall, B. Robert, R. J. Cogdell, H. Hashimoto

JOURNAL OF LUMINESCENCE 129 ( 12 ) 1808 - 1812 2009年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

We investigate how structural distortions in carotenoid cause decoherences of its high-frequency vibrational modes by applying the sub-20-fs time-resolved transient grating spectroscopy to beta-catotene and lycopene. The results indicate that the C = C central stretching mode shows significant loss of coherence under the effects of the steric hindrance between beta-ionone ring and polyene backbone, whereas the other high-frequency modes do not show such dependency on the structural distortions. (C) 2000 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jlumin.2009.04.098

Transient grating spectroscopy in photosynthetic purple bacteria Rhodobacter sphaeroides 2.4.1 査読

Mitsuru Sugisaki, Masazumi Fujiwara, Ritsuko Fujii, Katsunori Nakagawa, Mamoru Nango, Richard J. Cogdell, Hideki Hashimoto

JOURNAL OF LUMINESCENCE 129 ( 12 ) 1908 - 1911 2009年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The vibronic coherence of photosynthetic pigment-protein complexes has been investigated by means of transient grating spectroscopy using sub 20 fs optical pulses. In the present work, we focus our attention on the LH2 antenna complexes from Rhodobacter sphaeroides 2.4.1 because the information about their Structure investigated by the electron and atomic force microscopy is available and the electric levels of pigments are well resolved, resulting in clear absorption spectrum. The vibronic coherent oscillations with a period of a few tens of femtoseconds have been clearly observed We found that the temporal change of the coherent oscillations reflects the vibrational relaxation in the ground state. Calculations based on the Brownian oscillator model were performed Under the impulsive excitation limit. The spectral density has been determined from the Raman measurement of spheroidene. Good agreement between the calculation and the experimental results has been achieved in the linear absorption spectrum and transient grating signal, which strongly Supports the validity of our model. (C) 2009 Elsevier B.V. All rights reserved

DOI： 10.1016/j.jlumin.2009.01.027

Simultaneous reference and differential waveform acquisition in time-resolved terahertz spectroscopy 査読

Krzysztof Iwaszczuk, David G. Cooke, Masazumi Fujiwara, Hideki Hashimoto, Peter Uhd Jepsen

OPTICS EXPRESS 17 ( 24 ) 21969 - 21976 2009年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：OPTICAL SOC AMER

We present a new method for data acquisition in time-resolved terahertz spectroscopy experiments. Our approach is based on simultaneous collection of reference and differential THz scans. Both the optical THz generation beam and the pump beam are modulated at two different frequencies that are not harmonic with respect to each other. Our method allows not only twice as fast data acquisition but also minimization of noise connected to slowly varying laser power fluctuations and timing instabilities. Our use of the nonlinear crystal N-benzyl-2-methyl-4-nitroaniline (BNA) enables time-resolved THz spectroscopy to beyond 5 THz, thereby highlighting that the presented method is especially valuable at higher frequencies where phase errors in the data acquisition become increasingly important. (C) 2009 Optical Society of America

DOI： 10.1364/OE.17.021969

Simultaneous reference and differential waveform acquisition in time-resolved terahertz spectroscopy 査読

Krzysztof Iwaszczuk, David G. Cooke, Masazumi Fujiwara, Hideki Hashimoto, Peter Uhd Jepsen

OPTICS EXPRESS 17 ( 24 ) 21969 - 21976 2009年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：OPTICAL SOC AMER

We present a new method for data acquisition in time-resolved terahertz spectroscopy experiments. Our approach is based on simultaneous collection of reference and differential THz scans. Both the optical THz generation beam and the pump beam are modulated at two different frequencies that are not harmonic with respect to each other. Our method allows not only twice as fast data acquisition but also minimization of noise connected to slowly varying laser power fluctuations and timing instabilities. Our use of the nonlinear crystal N-benzyl-2-methyl-4-nitroaniline (BNA) enables time-resolved THz spectroscopy to beyond 5 THz, thereby highlighting that the presented method is especially valuable at higher frequencies where phase errors in the data acquisition become increasingly important. (C) 2009 Optical Society of America

DOI： 10.1364/OE.17.021969

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