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Journal Articles

High-efficiency contact grating fabricated on the basis of a Fabry-Perot type resonator for terahertz wave generation

Yoshida, Fumiko; Nagashima, Keisuke; Tsubouchi, Masaaki; Ochi, Yoshihiro; Maruyama, Momoko; Sugiyama, Akira

Japanese Journal of Applied Physics, 55(1), p.012201_1 - 012201_5, 2016/01

 Times Cited Count:6 Percentile:32.5(Physics, Applied)

Journal Articles

Yb:YAG thin-disk chirped pulse amplification laser system for intense terahertz pulse generation

Ochi, Yoshihiro; Nagashima, Keisuke; Maruyama, Momoko; Tsubouchi, Masaaki; Yoshida, Fumiko; Kono, Nanase; Mori, Michiaki; Sugiyama, Akira

Optics Express (Internet), 23(11), p.15057 - 15064, 2015/06

 Times Cited Count:22 Percentile:79.19(Optics)

We have developed a 1 kHz repetition picosecond laser system dedicated for intense terahertz (THz) pulse generation. The system comprises a chirped pulse amplification laser equipped with a Yb:YAG thin-disk amplifier. At room temperature, the Yb:YAG thin-disk regenerative amplifier provides pulses having energy of over 10 mJ and spectral bandwidth of 1.2 nm. The pulse duration achieved after passage through a diffraction grating pair compressor was 1.3 ps. By employing this picosecond laser as a pump source, THz pulses having a peak frequency of 0.3 THz and 4 $$mu$$J of energy were generated by means of optical rectification in an Mg-doped LiNbO$$_{3}$$ crystal.

Journal Articles

Intense THz pulse generation and its application

Tsubouchi, Masaaki

Shototsu, 12(2), p.36 - 54, 2015/03

A novel design for a contact grating device with an incorporated Fabry-Perot resonator is proposed for high-power terahertz light (THz) generation. We deposited a multilayer consisting of Ta$$_{2}$$O$$_{5}$$ and Al$$_{2}$$O$$_{3}$$ on a magnesium-doped stoichiometric LiNbO$$_{3}$$ substrate and fabricated grating grooves on the outermost layer. The multilayer was designed such that conditions for a Fabry-Perot resonator were satisfied for light diffracted by the grating. Consequently, the diffraction efficiency was enhanced by the resonator. The diffraction efficiency of the fabricated device was 71%. THz light generation was also demonstrated with the contact grating device.

Journal Articles

Current status of the driver laser system for intense terahertz wave generation

Tanaka, Momoko; Ochi, Yoshihiro; Kosuge, Atsushi; Okada, Hajime; Mori, Michiaki; Kiriyama, Hiromitsu; Tsubouchi, Masaaki; Nagashima, Keisuke

JAEA-Conf 2014-001, p.32 - 33, 2014/09

We have constructed a high power kHz laser system using Yb:YAG thin-disk as a gain medium for a driver laser of THz wave generation. A 4-bounce regenerative amplifier is constructed and output energy up to 10 mJ is obtained. Using compressed pulse, we demonstrated THz wave generation with LiNbO$$_{3}$$ crystal.

Journal Articles

Contact grating device with Fabry-Perot resonator for effective terahertz light generation

Tsubouchi, Masaaki; Nagashima, Keisuke; Yoshida, Fumiko; Ochi, Yoshihiro; Maruyama, Momoko

Optics Letters, 39(18), p.5439 - 5442, 2014/09

 Times Cited Count:32 Percentile:85.19(Optics)

A novel design for a contact grating device with an incorporated Fabry-Perot resonator is proposed for high-power terahertz light (THz) generation. We deposited a multilayer consisting of Ta$$_{2}$$O$$_{5}$$ and Al$$_{2}$$O$$_{3}$$ on a magnesium-doped stoichiometric LiNbO$$_{3}$$ substrate and fabricated grating grooves on the outermost layer. The multilayer was designed such that conditions for a Fabry-Perot resonator were satisfied for light diffracted by the grating. Consequently, the fraction of light transmitted into the LiNbO$$_{3}$$ substrate, i.e., the diffraction efficiency, was enhanced by the resonator. The diffraction efficiency of the fabricated device was 71%, which is close to the calculated value of 78% from the optimized design. THz light generation was also demonstrated with the contact grating device. The THz output of 0.41 microJ was obtained using NIR pump light of 2.7 mJ.

Journal Articles

Liquid-sheet jets for terahertz spectroscopy

Kondo, Masato*; Tsubouchi, Masaaki

Optics Express (Internet), 22(12), p.14135 - 14147, 2014/06

 Times Cited Count:13 Percentile:60.68(Optics)

We investigated liquid-sheet jets with controllable thickness for application to terahertz (THz) spectroscopy. Slit-type and colliding-jet nozzles were used to generate optically flat liquid jets. The thickness of the liquid sheet was determined precisely by spectral interference and THz time-domain-spectroscopy methods. By adjusting the collision angle of the colliding-jet nozzle, we could control the thickness of the liquid sheet from 50 to 120 $$mu$$m.

Journal Articles

Development of high-efficiency etalons with an optical shutter for terahertz laser pulses

Tsubouchi, Masaaki; Kumada, Takayuki

Optics Express (Internet), 20(27), p.28500 - 28506, 2012/12

 Times Cited Count:5 Percentile:29.36(Optics)

A high-efficiency etalon operated in the terahertz (THz) frequency region has been proposed to generate a THz pulse train. To achieve high-conversion efficiency to the pulse train, an optical shutter is employed in this etalon. The etalon is composed of a silicon (Si) plate as an input coupler and an indium-tin-oxide (ITO)-coated glass plate as an output coupler. After THz light is introduced into the etalon through the Si plate, the optical shutter pulse irradiates the Si surface to generate a photoconductive layer that acts as a highly reflective mirror for THz light. A THz pulse train and its comb-shaped spectrum have been realized by the use of the proposed etalon with the optical shutter. A finesse F of 9.04 was achieved at the spectral range of 75 GHz in this etalon.

Journal Articles

Terahertz tomography of a photo-induced carrier based on pump-probe spectroscopy using counterpropagation geometry

Tsubouchi, Masaaki; Nagai, Masaya*; Oshima, Yasuhiro*

Optics Letters, 37(17), p.3528 - 3530, 2012/09

 Times Cited Count:17 Percentile:65.03(Optics)

A novel technique for the terahertz (THz) tomography of a photo-induced carrier that is based on optical-pump THz-probe time-resolved reflection spectroscopy using counter-propagation geometry of the pump and probe pulses has been proposed. Transient reflection due to the photo-induced carrier provides information about the physical properties and spatial distribution separately. We have experimentally demonstrated this method using a silicon wafer. The obtained complex reflection can be reproduced by the exact solution of Maxwell's equations, assuming an exponential distribution of the photo-induced carrier density.

Journal Articles

Study on material science by using an intense laser

Akagi, Hiroshi; Itakura, Ryuji; Otobe, Tomohito; Kumada, Takayuki; Tsubouchi, Masaaki; Yokoyama, Atsushi

JAEA-Conf 2011-001, p.40 - 43, 2011/03

no abstracts in English

Journal Articles

Quantum control of molecular vibration and rotation toward the isotope separation

Yokoyama, Keiichi; Matsuoka, Leo; Kasajima, Tatsuya; Tsubouchi, Masaaki; Yokoyama, Atsushi

Proceedings of 5th Asian Symposium on Intense Laser Science (ASILS-5), p.113 - 119, 2009/05

The current status of the fundamental research for the quantum control conducted at Kansai Photon Science Institute are reported. In particular, the experimental studies on vibrational control of diatomic molecules, the nitrogen molecules and the iodine molecules, and the theoretical study on the rotational control of the diatomic molecule, the cesium iodide molecule (CsI), are introduced. For the study of vibrational control of N$$_{2}$$, the vibration selective excitation with extremely broadband white light pulses is demonstrated by tuning the time interval of a linearly chirped white light pulse pair. For the study of vibrational control of I$$_{2}$$, the direction control of stimulated impulsive Raman transition is demonstrated by changing the sign of the chirp rate. For the study of rotational control of CsI, the isotope-selective population distribution transfer is demonstrated numerically using frequency comb in the terahertz-wave region.

Oral presentation

Double pulse generation and detection in THz region; Simplest case of arbitrary pulse shaping

Tsubouchi, Masaaki; Yokoyama, Keiichi; Sugiyama, Akira

no journal, , 

In this study, we examined the double pulse generation of THz pulses which is the simplest example toward the arbitrary pulse shaping. Intrinsic difficulties of THz pulse shaping was found from the double pulse experiment.

Oral presentation

Annual progress and future plans of Laser R&D Group

Sugiyama, Akira; Kiriyama, Hiromitsu; Ochi, Yoshihiro; Tanaka, Momoko; Nakai, Yoshiki; Sasao, Hajime; Tateno, Ryo; Okada, Hajime; Kosuge, Atsushi; Tsubouchi, Masaaki

no journal, , 

The main subject of our group is upgrade of J-KAREN and TOPAZ laser systems. The J-KAREN achieves the potential for generating a peak power of 500 TW, and exceeds a contrast ratio of 10E10. The TOPAZ achieves pulse power of 15 J at a repetition rate of 0.1 Hz. We also started a development of another laser system named QUADRA (Quality Ultra ADvanced RAdiation Source) in C-Phost. The QUADRA system is a high averaged short pulse laser pumped by high power LD at kHz repetition rate. This development is essential for the developments of other new laser systems in the next 5-year program of JAEA.

Oral presentation

Double pulse generation and detection in THz region; The Simplest case of arbitrary pulse shaping

Tsubouchi, Masaaki; Yokoyama, Keiichi; Sugiyama, Akira

no journal, , 

no abstracts in English

Oral presentation

Theoretical study on the isotope-selective vibrational ladder climbing by consecutive stimulated Raman transitions

Kasajima, Tatsuya; Tsubouchi, Masaaki; Matsuoka, Leo; Yokoyama, Keiichi; Yokoyama, Atsushi

no journal, , 

no abstracts in English

Oral presentation

Theoretical study on the cascade excitation based on pure rotational transition in diatomic molecules

Yokoyama, Keiichi; Matsuoka, Leo; Akagi, Hiroshi; Kasajima, Tatsuya; Tsubouchi, Masaaki

no journal, , 

Pure rotational transition shows evenly spaced line spectra, the rotational comb, when the molecule is diatomic and has a closed-shell electronic structure. Let us consider irradiating an optical frequency comb tuned to the rotational comb. We studied numerically the dynamics of the molecular rotation in such a irradiation. As a result, the dynamics was found to obey the diffusion equation within the quantum mechanics. Also, we found that an isotope-selective excitation based on this scheme is a novel example of coherent control effective even at high temperature.

Oral presentation

Isotope-selective vibrational ladder climbing by linearly chirped pulse pair

Kasajima, Tatsuya; Tsubouchi, Masaaki; Yokoyama, Keiichi

no journal, , 

no abstracts in English

Oral presentation

Studies for isotope separation of radioactive waste

Yokoyama, Keiichi; Kasajima, Tatsuya; Matsuoka, Leo; Hashimoto, Masashi; Tsubouchi, Masaaki; Sugiyama, Akira; Yokoyama, Atsushi

no journal, , 

Technological innovation in the isotope separation of long-lived fission products is demanded. Quantum control may provide a breakthrough in such technology. Recently, we proposed a novel scheme based on cascaded excitation of rotation in diatomic molecules. Both (1) demonstration of quantum walk by Raman transition using a conventional Ti:Sapphire laser and (2) development of high-power terahertz-wave source are concurrently proceeded. (1) Cascaded excitation of rotation in the nitrogen molecule N$$_{2}$$ will be induced by impulsive Raman transitions. At present, we are developing a method to observe the incoherent population distribution among rotational states, which involves femotosecond coherent anti-Stokes Raman scattering. Also, current status of (2) development of high-power terahertz-wave source will be briefly introduced, including optical rectification in ZnTe and LiNbO$$_{3}$$ crystals and a plan for construction of a high-power, picosecond laser as a driver laser.

Oral presentation

A New scheme for the laser isotope separation applicable to heavy elements

Yokoyama, Keiichi; Matsuoka, Leo; Kasajima, Tatsuya; Tsubouchi, Masaaki; Hashimoto, Masashi

no journal, , 

Recent progress in laser science enables us precise manipulation of molecules by taking advantages of the wave nature of matter. These techniques are called coherent quantum control. Using coherent quantum control, a breakthrough in laser isotope separation may be realized. Actually, we proposed a novel scheme of isotope selective excitation, which is based on cascaded excitation of rotation in diatomic molecules. A numerical simulation done by solving a coupled Schroedinger equation for the cesium iodide molecule has shown that the separation factor reaches three orders of magnitude higher than that by the conventional scheme. The current status of the experimental demonstration undergoing in our institute will be introduced.

Oral presentation

Ultrafast optical pump - THz probe time-resolved spectroscopy on Si

Tsubouchi, Masaaki; Yokoyama, Atsushi; Nagai, Masaya*; Oshima, Yasuhiro*

no journal, , 

no abstracts in English

Oral presentation

Time-resolved vibrational CARS for measurement of rotational state distribution

Kasajima, Tatsuya; Tsubouchi, Masaaki; Matsuoka, Leo; Yokoyama, Keiichi

no journal, , 

no abstracts in English

71 (Records 1-20 displayed on this page)