Sub-picosecond regenerative amplifier of Yb-doped YO ceramic thin disk

Maruyama, Momoko; Okada, Hajime; Ochi, Yoshihiro; Nagashima, Keisuke

Optics Express (Internet), 24(2), p.1685 - 1692, 2016/01

https://doi.org/10.1364/OE.24.001685

We have developed a 1 kHz regenerative amplifier using an Yb:YO ceramic thin disk as the gain medium. Furthermore, the thermal conductivity and heat generation property of Yb: YO ceramic were investigated. In the developed regenerative amplifier, a laser beam is bounced off the thin disk six times in each round trip. The output energy is over 2 mJ, spectral bandwidth is 1.8 nm at FWHM, and pulse duration after pulse compression is 0.9 ps.

Demonstration of the high collection efficiency of a broadband Mo/Si multilayer mirror with a graded multilayer coating on an ellipsoidal substrate

Ichimaru, Satoshi*; Takenaka, Hisataka*; Namikawa, Kazumichi*; Gullikson, E. M.*; Maruyama, Momoko; Oku, Satoshi*

Review of Scientific Instruments, 86(9), p.093106_1 - 093106_7, 2015/09

https://doi.org/10.1063/1.4929708

A graded and broadband Mo/Si multilayer mirror for EUV spectroscopy is demonstrated. This mirror has an average reflectivity profile of 16% in the wavelength region from 15 nm to 17 nm and an effective area of 1100 - 1500 mm. This reflectivity is about 4 times larger than that of a standard Mo/Si multilayer mirror on a 1 in. diameter substrate, showing that the mirror can be used for measuring EUV fluorescence at wavelengths in the region around 15 nm to 17 nm.

High spatial resolution ZnO scintillator for an in situ imaging device in EUV region

Arita, Ren*; Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Empizo, M.*; Hori, Tatsuhiro*; Fukuda, Kazuhito*; Minami, Yuki*; Sarukura, Nobuhiko*; Maruyama, Momoko; et al.

Optical Materials, 36(12), p.2012 - 2015, 2014/10

https://doi.org/10.1016/j.optmat.2014.01.031

A single shot image of a ZnO crystal excited by the EUV laser of Kansai Photon Science Institute was captured. The evaluated EUV beam waist radii from the ZnO emission pattern along the horizontal and vertical axes are 5.0 and 4.7m, respectively. The expected focal spot size of EUV laser and the spatial resolution of the magnifier (including the Schwarzschild objectives and lenses) are however 1 and 4m, respectively. The discrepancy on the spatial resolutions is attributed to exciton diffusion. We estimated the ZnO exciton diffusion length from the effective decay time which is shortened by exciton-exciton collision quenching and which is dependence on excitation energy density. Our results indicate that the short lifetime of ZnO is required to improve the spatial resolution.

Picosecond view of microscopic-scale polarization clusters in paraelectric BaTiO

Tai, R.; Namikawa, Kazumichi; Sawada, Akikatsu*; Kishimoto, Maki; Tanaka, Momoko; Lu, P.*; Nagashima, Keisuke; Maruyama, Hiroshi*; Ando, Masami*

Physical Review Letters, 93(8), p.087601_1 - 087601_4, 2004/08

A2004-0483.pdf:0.43MB

https://doi.org/10.1103/PhysRevLett.93.087601

The polarization clusters existing in both the ferroelectric and the paraelectric phase of BaTiO are directly observed and characterized for the first time by a picosecond soft X-ray laser speckle technique. These dynamic clusters appear continuously across the Curie temperature Tc. The clusters' distance increases approximately linearly with temperature, while their mean size does not change significantly. The polarization exhibits a maximum at a temperature about 5 degree above Tc. The clusters' short-range correlation strength diverges as (T-Tc)0.410.02 as temperature decreases toward Tc.

QUADRA-T; A Driver laser system for intense THz pulse generation

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

no journal, , 

We have developed a high average power picosecond laser system, named QUADRA-T, dedicated to intense terahertz (THz) pulse generation. QUADRA-T is a chirped pulse amplification laser equipping Yb:YAG thin-disk amplifier. The Yb:YAG thin-disk regenerative amplifier at room temperature provides 10 mJ pulses at a repetition rate of 1 kHz. Duration of a recompressed pulse is 1.3 ps. By employing this picosecond pulse as a pump source, THz pulse of the center frequency of 0.3 THz with a few micro joules energy has been obtained by the optical rectification in Mg-LiNbO crystal.

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.

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

Ablation mechanism and some ideas of applications of modified surface structures induced by picosecond soft X-ray laser

Ishino, Masahiko; Hasegawa, Noboru; Nishikino, Masaharu; Maruyama, Momoko; Faenov, A.*; Tamotsu, Satoshi*; Pikuz, T.*; Inogamov, N.*; Skobelev, I.*; Kawachi, Tetsuya; et al.

no journal, , 

Soft X-ray laser pulses having a wavelength of 13.9 nm and a duration of 7 ps have an ability to make various nanometer scale damage structures on material surfaces. Our experimental study confirms the theoretical model of an atomistic simulation, which predicts the splash of molten layers occurring under a low electron temperature less than 1 eV and creating nanometer scale surface modifications. We also propose the probable ideas of applications of surface structures induced by the soft X-ray laser pulses. Catalytic substrates for chemical reactions, nanopillar sheet for culturing biological cells, and geometrical structures beneath the surface will be candidates. When we can control the surface modification process, the soft X-ray laser beam will enable us to fabricate three dimensional nanometer scale structures.

Contact grating device with fabry-perot resonator for effective THz light generation

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 80%. THz light generation was also demonstrated with the contact grating device.

Upgrade of QUADRA-T

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

no journal, , 

We will present of preliminary result of multi-pass amplification using Yb:YAG thin-disk medium for QUADRA-T.