Browsing by Author "Teramoto, Takahiro"

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Clean sub-8-fs pulses at 400 nm generated by a hollow fiber compressor for ultraviolet ultrafast pump-probe spectroscopy
(2010-09-27)
Liu, Jun
;
Okamura, Kotaro
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Kida, Yuichiro
;
Teramoto, Takahiro
;
Kobayashi, Takayoshi
Clean 7.5 fs pulses at 400 nm with less than 3% energy in tiny satellite pulses were obtained by spectral broadening in a hollow fiber and dispersive compensating using a prism pair together with a deformable mirror system. As an example, this stable and clean pulse was used to study the ultrafast pump-probe spectroscopy of photoactive yellow protein. Moreover, the self-diffraction signal shows a smoothed and broadened laser spectrum and is expected to have a further clean laser pulse, which makes it more useful in the ultrafast pump-probe spectroscopy in the future. (C) 2010 Optical Society of America
Development of real-time vibrational spectroscopy of molecules in electronic excited states: toward mapping molecular potential energy hypersurfaces
(2011-05-01)
Teramoto, Takahiro
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Du, Juan
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Wang, Zhuan
;
Liu, Jun
;
Tokunaga, Eiji
We have developed an experimental system for real-time vibrational spectroscopy of molecules in a specific electronic excited state. A synchronized UV light source and a few-cycle visible laser pulse were utilized to prepare and investigate the ultrafast dynamics of molecules in the electronic excited states. A multichannel lock-in amplifier detection system operating in a tandem double lock-in detection mode was used to extract the signal correlated only to the UV and visible pump pulses. Real-time vibrational spectroscopy of chrysene in the triplet state and 1', 3'-dihydro-1', 3', 3'-trimethyl-6-nitrospiro [2H-1-benzopyran-2, 2'-(2H)-indole] in a photochromic state was demonstrated. (C) 2011 Optical Society of America
Generation of stable sub-10 fs pulses at 400 nm in a hollow fiber for UV pump-probe experiment
(2010-03-01)
Liu, Jun
;
Kida, Yuichiro
;
Teramoto, Takahiro
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Kobayashi, Takayoshi
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電子物理學系
Stable sub-10-fs pulses useful for many pump-probe experiments with center wavelength at 400 nm were obtained using a hollow-fiber compression technique with a beam-pointing stabilizing system. The output power stability was improved by around 2-times with the beam-pointing stabilizer. A 1-mm-thick cell sample of perylene dissolved in cyclohexane was used to test the pulse using for the pump-probe experiment. Even the high C-H stretching of vibration mode at around 2860 cm(-1), 2916 cm(-1), and 2955 cm(-1) were real-time resolved with vibrational phase information. (C) 2010 Optical Society of America
Multiple mode coupling in Cy3 molecules by impulsive coherent vibrational spectroscopy using a few-cycle laser pulse
(2010)
Teramoto, Takahiro
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Kobayashi, Takayoshi
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電子物理學系
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Department of Electrophysics
Multiple vibrational mode coupling that induces the missing mode effect and Duschinsky rotation on the potential energy surface of the S(1) state in the Cy(3) molecule was clarified by real-time ultrafast spectroscopy with a few-cycle laser pulse. The contributions of homogeneous and inhomogeneous dephasing to the total dephasing time were found to be 55% and 45%, respectively.
Real-Time Vibrational Dynamics in Chlorophyll a Studied with a Few-Cycle Pulse Laser
(2011-08-17)
Du, Juan
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Teramoto, Takahiro
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Nakata, Kazuaki
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Tokunaga, Eiji
;
Kobayashi, Takayoshi
We use a 6.8-fs laser as the light source for broad-band femtosecond pump-probe real-time vibrational spectroscopy to investigate both electronic relaxation and vibrational dynamics of the Q(y)-band of Chl-a at 293 K. More than 25 vibrational modes coupled to the Q(y) transition are observed. Eleven of them have been clarified predominantly due to the excited state, and six of them are concluded to be nearly exclusively resulting from the ground-state wave-packet motion. Moreover, thanks to the broad-band detection over 5000 cm(-1), the modulated signals due to the excited state vibrational coherence are observed on both sides of the 0-0 transition with equal separation. The corresponding nonlinear process has been studied using a three-level model, from which the probe wavelength dependence of the phase of the periodic modulation can be calculated. The probe wavelength dependence of the vibrational amplitude is interpreted in terms of the interaction between the "pump" or "laser," Stokes, and anti-Stokes field intermediated by the molecular vibrations. In addition, an excited state absorption peak at similar to 709 nm has been observed. To the best of our knowledge, this is the first study of broad-band real-time vibrational spectroscopy in Chl-a.
Simultaneous compression and amplification of a laser pulse in a glass plate
(2010-02-01)
Liu, Jun
;
Kida, Yuichiro
;
Teramoto, Takahiro
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Kobayashi, Takayoshi
;
電子物理學系
We demonstrated a novel method of simultaneous compression and amplification of a weak laser pulse in a glass plate using cross-phase modulation in conjunction with four-wave optical parametric amplification that was pumped by an intense femtosecond pulse. A proof-of-principle experiment succeeded in smooth broadening of the weak pulse spectrum by a factor of about three and simultaneously amplifying the pulse energy by more than three times. By using chirped mirrors to compensate the dispersion, the weak pulse was compressed from 22.6 fs to 12.6 fs. Furthermore, the output spectrum of seed pulse could be tuned by varying the delay of the intense pump pulse with respect to the weak seed pulse. This method can also be used for simultaneous spectral broadening of several weak beams with different wavelength at the same time. (C) 2009 Optical Society of America
The observation of strong dynamic electron-phonon couplings due to a breather state in trans-polyacetylene
(2009)
Teramoto, Takahiro
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Wang, Zhuan
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Kobryanskii, Valerii M.
;
Taneichi, Takashi
;
Kobayashi, Takayoshi
The dynamics preceding the separation process of a charged soliton pair after photoexcitation in trans-polyacetylene was successfully time-resolved using ultrafast spectroscopy with a few-optical-cycle laser. It was directly verified that after photoexcitation, the electron-hole pair relaxes with a breather mode as theory predicts with an electron-hole pair lifetime of 33-50 fs, which is in agreement with the electronic dephasing time. By applying the spectrogram analysis to the time trace of the absorbance change, the ultrafast amplitude and frequency modulations of C-C and C=C stretching modes lasting only shorter than 100 fs induced by breather modes can be observed simultaneously for the first time. The frequency shift of C-C and C=C stretching modes caused by the breather mode are observed in good agreement with the SSH Hamiltonian. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Ultrafast real-time vibronic coupling dynamics of a breather soliton in trans-polyacetylene with a few-optical-cycle-pulse laser
(2009-09-01)
Kobayashi, Takayoshi
;
Teramoto, Takahiro
;
Kobryanskii, Valerii M.
;
Taneichi, Takashi
;
電子物理學系
The dynamics preceding the spatial separation of a charged soliton pair after photoexcitation in trans-polyacetylene was successfully investigated by using ultrafast spectroscopy with a 6.2 fs pulse laser. It was directly verified that after photoexcitation, the electron-hole pair relaxes with a breather mode (i.e. multi-quanta vibronic states), as theory predicts, with an electron-hole pair lifetime of 33-50 fs. By applying spectrogram analysis to the time trace of the absorbance change, the ultrafast amplitude and frequency modulations of C-C and C=C stretching modes, induced by breathers and lasting no longer than 100 fs, can be observed Simultaneously for the first time. The frequency shifts of both modes were in good agreement with a simulation based on the Su-Schrieffer-Heeger model. It was found that the intensities of transition dipoles changed due to breathers, whereas transition energies were dominantly modulated by C=C stretching modes as recent theoretical work predicted. (C) 2009 Elsevier B.V. All rights reserved.
Ultrafast real-time vibronic coupling of a breather soliton in trans-polyacetylene using a few cycle pulse
(2009-01-01)
Kobayashi, Takayoshi
;
Teramoto, Takahiro
;
Kobryanskii, Valerii M.
;
Taneichi, Takashi
;
電子物理學系
The ultrafast electron-phonon coupling dynamics due to a breather soliton inducing amplitude and frequency modulations after photoexcitation in trans-polyacetylene was observed by ultrafast multicolor spectroscopy. The results were in good agreement with recent theoretical predictions. (C) 2009 Optical Society of America
Ultrafast real-time vibronic coupling of a breather soliton in trans-polyacetylene using a laser pulse with few cycles
(2009-01-01)
Teramoto, Takahiro
;
Wang, Zhuan
;
Kobryanskii, Valerii M.
;
Taneichi, Takashi
;
Kobayashi, Takayoshi
Simultaneous modulations of both frequencies and amplitudes of C-C and C=C stretching vibration modes, due to dynamical coupling to a breather soliton, in trans-polyacetylene was successfully time resolved. The frequency shifts of both modes were in good agreement with a simulation based on the Su-Schrieffer-Heeger model. It was found that the intensities of transition dipoles changed due to the breather, whereas transition energies were dominantly modulated by C=C stretching mode as recent theoretical work predicted.