None

Onoe, Hironori*; Yoshida, Fumiko*; Hirota, Shogo*; Sudo, Yuko*; Saegusa, Hiromitsu*; Ishida, Keisuke*; Sawada, Atsushi

NUMO-TR-25-03, p.105 - 111, 2025/10

no abstracts in English

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

https://doi.org/10.7567/JJAP.55.012201

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

https://doi.org/10.1364/OL.39.005439

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 TaO and AlO on a magnesium-doped stoichiometric LiNbO 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 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.

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.

Contact grating device with Fabry-Perot resonator toward intense THz pulse generation by optical rectification

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

no journal, , 

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 TaO and AlO on a magnesium-doped stoichiometric LiNbO 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.

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 rutile crystal, which has the highest refractive index within oxidized materials. However, there are no TiO 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 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 thin film with a high refractive index, and low coefficients of absorption and scattering. The highest refractive index was achieved by this method.

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 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).

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 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).

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

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.