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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:37.08(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:20 Percentile:79.2(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

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:28 Percentile:84.76(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

Preparation of a dense TiO$$_{2}$$ thin film by oxidizing metallic titanium

Yoshida, Fumiko; Tanaka, Momoko; Nagashima, Keisuke

Thin Solid Films, 537, p.23 - 27, 2013/06

 Times Cited Count:2 Percentile:11.91(Materials Science, Multidisciplinary)

Journal Articles

Development of LBB assessment method for Japan Sodium Cooled Fast Reactor (JSFR) pipes, 4; Verification of crack opening displacement assessment method for thin wall pipes made of Mod.9Cr-1Mo steel

Wakai, Takashi; Machida, Hideo*; Yoshida, Shinji*; Kawashima, Fumiko*; Kikuchi, Koichi*; Xu, Y.*; Tsukimori, Kazuyuki

Proceedings of 2011 ASME Pressure Vessels and Piping Conference (PVP 2011) (CD-ROM), 10 Pages, 2011/07

This paper describes the improved COD assessment method and verifies the validity of the method based on the results of a series of four-point bending tests at elevated temperature using thin wall modified 9Cr-1Mo steel pipe containing a circumferential through wall crack. As a result, COD values calculated by the proposed method were in a good agreement with the experimental results for the uniform pipe without weld. In the case that the crack was machined at weld metal or heat affected zone (HAZ), proposed method predicted relatively larger COD than the experimental results. The causes of such discrepancies were discussed comparing with the results of finite element analyses. Based on these examinations, the rational leak rate evaluation method in LBB assessment was proposed.

Oral presentation

Development of kHz regenerative amplifier using Yb:YAG thin disk

Ochi, Yoshihiro; Okada, Hajime; Nagashima, Keisuke; Kosuge, Atsushi; Tanaka, Momoko; Kiriyama, Hiromitsu; Mori, Michiaki; Yoshida, Fumiko; Kong, W.*; Taira, Takunori*

no journal, , 

At Kansai Photon Science Institute, we develop new laser system using Yb:YAG thin-disk as a driver for generating intense THz wave. Specifications of the laser are 1030 nm in wavelength, 1 kHz repetition, 1 ps duration, and 100 mJ in energy, respectively. The laser system consists of two amplifiers; the first is regenerative amplifier and the second is multi-pass amplifier. At the conference, I will present the current status of the regenerative amplifier.

Oral presentation

Development of high temporal and spatial quality, high intensity laser system

Kiriyama, Hiromitsu; Ochi, Yoshihiro; Mori, Michiaki; Tanaka, Momoko; Okada, Hajime; Kosuge, Atsushi; Yoshida, Fumiko; Shimomura, Takuya; Sasao, Hajime; Nakai, Yoshiki*; et al.

no journal, , 

We describe two specific high intensity laser systems that are being developed in our laboratory for many applications such as high field science and nonlinear optics. We report on an ultra-high intensity petawatt-class Ti:sapphire chirped-pulse amplification laser system that can produce a pulse energy of $$sim$$ 18 J with $$sim$$ 30 fs pulse duration for studying extremely high intensity laser matter interaction process and a small-scaled Yb:YAG chirped-pulse amplification laser system that can generate a pulse energy of $$sim$$ 100 m J of $$sim$$ 500 fs pulse duration for compact, high efficiency, high repetition system. We discuss the basic design aspects and present the results from our experimental investigations of these laser systems.

Oral presentation

Development of a new device with contact grating for terahertz wave generation

Yoshida, Fumiko; Tanaka, Momoko; Nagashima, Keisuke

no journal, , 

We have proposed a new device with contact grating for intense terahertz wave generation. It is important to prepare the contact grating with a high refractive index material because high diffraction efficient is expected with higher refractive index. Therefore, we focused on TiO$$_{2}$$ rutile crystal, which has the highest refractive index within oxidized materials. However, there are no TiO$$_{2}$$ rutile thin films with higher refractive index than 2.5 at about 1 um. We adopted a method of oxidizing a Ti thin film, in which a Ti thin film was deposited by electronbeam evaporation and annealed in air for crystallization to a rutile crystal. Various TiO$$_{2}$$ thin films were prepared under different conditions. The annealing temperature, annealing time, and heating rate of the Ti thin films were optimized to obtain a transparent TiO$$_{2}$$ thin film with a high refractive index, and low coefficients of absorption and scattering. The highest refractive index was achieved by this method.

Oral presentation

Coherent anti-Stokes Raman scattering from aligned nitrogen molecules

Yoshida, Fumiko; Matsuoka, Leo; Yokoyama, Keiichi

no journal, , 

Oral presentation

Displacement of rotational-state distribution in diatomic molecules with a train of femtosecond laser pulses

Yoshida, Fumiko; Kasajima, Tatsuya*; Matsuoka, Leo; Yokoyama, Keiichi

no journal, , 

Oral presentation

Development for intense THz light generation in KPSI

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

no journal, , 

In KPSI, we are developing the intense THz light generation apparatus. In this presentation, we will introduce the current status of the developing the apparatus, including the pump laser system, THz generation and detection system, and so on. The pulse shaping is also important for the practical use of the THz light. As the first step, we have developed the THz etalon with an optical shutter.

Oral presentation

Development of intense THz light source, 2; Generation of THz light

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

no journal, , 

We have developed high repetition (1 kHz) intense THz laser light source for the molecular axis control by non-linear interaction between intense THz light and molecules.

Oral presentation

Coherent anti-Stokes Raman scattering from aligned nitrogen molecules

Yoshida, Fumiko; Yokoyama, Keiichi

no journal, , 

Oral presentation

Generation of high power THz light for control of molecular rotation

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

no journal, , 

We are developing intense THz light source to realize control of molecular axis orientation in space. From the theoretical studies by Hebling and co-workers, it has been known that the desirable excitation NIR pulse for the THz light generation process in the Mg-sLiNbO$$_{3}$$ crystal should have the pulse width of 400 fs - 1 ps, and the tilted pulse front by 63 degree. To generate such NIR light, the Yb:YAG based amplifier system is one of the good candidates. By using this system, we are trying to generate the intense THz light with the high repetition rate (1 kHz).

Oral presentation

Development of intense THz light source, 1; Driver laser system and probe pulse generation

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

no journal, , 

We will present current status of a driver laser system for intense THz wave generation. The driver laser system, QUADRA-T, is a 1 kHz repetition CPA laser equipped with Yb:YAG thin disk amplifier. Current output power from a regenerative amplifier is about 10 W (10 mJ/pulse). Upgrade to 100W class power output using a multi-pass amplifier is the next plan.

Oral presentation

Development of intense THz laser light for control of molecules

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

no journal, , 

We are developing intense THz light source to realize control of molecular axis orientation in space. From the theoretical studies by Hebling and co-workers, it has been known that the desirable excitation NIR pulse for the THz light generation process in the Mg-sLiNbO$$_{3}$$ crystal should have the pulse width of 400 fs $$sim$$ 1 ps, and the tilted pulse front by 63 degree. To generate such NIR light, the Yb:YAG based amplifier system is one of the good candidates. By using this system, we are trying to generate the intense THz light with the high repetition rate (1 kHz).

Oral presentation

Development of intense THz light for control of molecules

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

no journal, , 

The nonlinear interaction between terahertz (THz) light and matter has recently been of interest for its availability to control molecular alignment in space. The pulse train of the intense THz light is one of the candidates to align the molecules efficiently and nondestructively. In this study, we have developed the experimental apparatus to generate the intense THz light. The THz etalon to generate the THz pulse train has been presented in our previous study.

Oral presentation

High average power laser from Yb:YAG thin-disk amplifiers and its applications

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

no journal, , 

We are developing a high average power laser system using Yb:YAG thin-disk amplifiers. Currently picoseconds pulses with 10 mJ energy are delivered from the regenerative amplifier at repetition rate of 1 kHz. The pulse energy will increase up to 100 mJ by a Yb:YAG thin-disk multi-pass amplifier. The picosecond pulses have been used in several applications such as intense THz light wave generation, laser induced damage test, and so on. I will present details of the laser system and preliminary results of applications.

Oral presentation

Generation of high power THz light by contact grating method

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

no journal, , 

The nonlinear interaction between terahertz (THz) light and matter has recently been of interest for its availability to control molecular alignment in space. The pulse train of the intense THz light is one of the candidates to align the molecules efficiently and nondestructively. In this study, we have developed the experimental apparatus to generate the intense THz light. The THz etalon to generate the THz pulse train has been presented in our previous study

36 (Records 1-20 displayed on this page)