Browsing by Author "Kida, Yuichiro"

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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
;
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
Femtosecond pulses cleaning by transient-grating process Kerr-optical media
(2011-05-10)
Liu, Jun
;
Okamura, Kotaro
;
Kida, Yuichiro
;
Kobayashi, Talcayoshi
;
電子物理學系
We use a transient-grating (TG) process in a Kerr bulk medium to clean a femtosecond laser pulse. Using the technique, the temporal contrast of the generated TO signal is improved by more than two orders of magnitude in comparison with the incident pulse in a 0.5-mm-thick fused silica plate. The laser spectrum is smoothed and broadened, and the pulse duration is shortened simultaneously. We expect to extend this technique to a clean pulse with broadband spectral bandwidth at a wide spectral range because it is a phase-matched process.
Femtosecond pulses cleaning by transient-grating process Kerr-optical media
(2011-05-10)
Liu, Jun
;
Okamura, Kotaro
;
Kida, Yuichiro
;
Kobayashi, Talcayoshi
;
電子物理學系
We use a transient-grating (TG) process in a Kerr bulk medium to clean a femtosecond laser pulse. Using the technique, the temporal contrast of the generated TO signal is improved by more than two orders of magnitude in comparison with the incident pulse in a 0.5-mm-thick fused silica plate. The laser spectrum is smoothed and broadened, and the pulse duration is shortened simultaneously. We expect to extend this technique to a clean pulse with broadband spectral bandwidth at a wide spectral range because it is a phase-matched process.
Generation and Optimization of Femtosecond Pulses by Four-Wave Mixing Process
(2012-01-01)
Kobayashi, Takayoshi
;
Liu, Jun
;
Kida, Yuichiro
;
電子物理學系
;
Department of Electrophysics
Four-wave mixing (FWM) was used to generate and optimize ultrashort pulses with wavelengths from ultraviolet (UV) to near-infrared in bulk media and gases. Wavelength-tunable multicolored pulses were simultaneously generated by cascaded FWM in glass plates. By using incident chirped pulses, 15-fs self-compressed multicolored pulses were obtained with excellent properties. Self-compression was also used to generate ultrashort deep-UV (DUV) pulses. The positive frequency chirp in a self-phase-modulated pulseissuitable for this objective. Sub-10-fs DUV pulses were generated without using any additional pulse compressors. Self-diffraction was used to clean the pulse, broaden the spectrum, and enhance the spatial beam quality. These multicolored pulses can be simultaneously amplified and compressed by a four-wave optical parametric amplifier. The generated multicolored pulses are useful for multicolored ultrafast spectroscopy, microscopy experiments, and as seeds for petawatt lasers with high temporal contrasts.
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
;
Kobayashi, Takayoshi
;
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
Generation of sub-10 fs ultraviolet Gaussian pulses
(2011-01-01)
Kida, Yuichiro
;
Kobayashi, Takayoshi
;
電子物理學系
;
Department of Electrophysics
A technique is proposed for generating sub-10 fs deep ultraviolet (DUV) pulses with Gaussian temporal and spectral profiles. In this approach, a broadband DUV pulse with a negative frequency chirp is generated and compressed by normal group-velocity dispersion in a transparent medium. The pulse shape is not significantly distorted by high-order spectral phase distortion. In principle, nearly transform-limited sub-6 fs UV pulses with pulse energies of several tens of microjoules are expected to be generated. Numerical simulations indicate that a Ti:sapphire chirped-pulse amplifier with a pulse energy of several millijoules and a pulse duration of 35 fs can be used to generate high-energy sub-6 fs UV pulses. The technique is partially demonstrated by an experiment using a low-power Ti: sapphire chirped-pulse amplifier to generate low-energy sub-10 fs single DUV pulses with waveforms that quantitatively agree with those predicted by the numerical simulations. This technique can be used to generate high-energy sub-10 fs DUV pulses with Gaussian temporal and spectral profiles for ultrafast spectroscopy in the gas phase as well as the liquid and solid phases. (C) 2010 Optical Society of America
Simultaneous compression and amplification of a laser pulse in a glass plate
(2010-02-01)
Liu, Jun
;
Kida, Yuichiro
;
Teramoto, Takahiro
;
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
Sub-10-fs deep-ultraviolet light source with stable power and spectrum
(2012-09-10)
Kida, Yuichiro
;
Okamura, Kotaro
;
Liu, Jun
;
Kobayashi, Takayoshi
;
電子物理學系
In some applications of ultrafast spectroscopy that employ sub-10-fs pulses, the pulse spectrum and power need to be stable for several tens of minutes. In this study, we generate sub-10-fs deep-ultraviolet (DUV) pulses with such stabilities by chirped-pulse four-wave mixing. A power fluctuation of less than 3% rms was realized by employing stabilization schemes that employ a power stabilizer. The pulses generated in this study have been applied to transient absorption spectroscopy in the DUV with a sub-10-fs time resolution [Phys. Chem. Chem. Phys. 14, 6200 (2012).]. This sub-10-fs DUV source has a similar performance to widely used noncollinear optical parametric amplifiers. (c) 2012 Optical Society of America
Temporal contrast enhancement of femtosecond pulses by a self-diffraction process in a bulk Kerr medium
(2010-10-11)
Liu, Jun
;
Okamura, Kotaro
;
Kida, Yuichiro
;
Kobayashi, Takayoshi
;
電子物理學系
We demonstrated for the first time the application of a self-diffraction (SD) process in a bulk Kerr medium to improve the temporal, spectral, and spatial qualities of femtosecond laser pulses. A proof-of-principle experiment succeeded in improving the temporal contrast of a femtosecond pulse by four orders of magnitude even in the picosecond region using a 0.5-mm-thick fused silica glass plate by this technique. The energy conversion efficiency from the incident pulses to the two first-order SD signals is about 12%. By the SD process, a laser pulse with smoother spectral shape, higher beam quality, and shorter pulse duration than those of the input pulse was generated. This technique is expected to be used to design background-free petawatt laser system in the future. (C) 2010 Optical Society of America
Ultrafast spectroscopy with sub-10 fs deep-ultraviolet pulses
(2012)
Kobayashi, Takayoshi
;
Kida, Yuichiro
;
電子物理學系
;
Department of Electrophysics
Time-resolved transient absorption spectroscopy with sub-9 fs ultrashort laser pulses in the deep-ultraviolet (DUV) region is reported for the first time. Single 8.7 fs DUV pulses with a spectral range of 255-290 nm are generated by a chirped-pulse four-wave mixing technique for use as pump and probe pulses. Electronic excited state and vibrational dynamics are simultaneously observed for an aqueous solution of thymine over the full spectral range using a 128-channel lock-in detector. Vibrational modes of the electronic ground state and excited states can be observed as well as the decay dynamics of the electronic excited state. Information on the initial phase of the vibrational modes is extracted from the measured difference absorbance trace, which contains oscillatory structures arising from the vibrational modes of the molecule. Along with other techniques such as time-resolved infrared spectroscopy, spectroscopy with sub-9 fs DUV pulses is expected to contribute to a detailed understanding of the photochemical dynamics of biologically significant molecules that absorb in the DUV region such as DNA and amino acids.