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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:34.28(Physics, Applied)

Journal Articles

Sub-picosecond regenerative amplifier of Yb-doped Y$$_{2}$$O$$_{3}$$ ceramic thin disk

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

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

 Times Cited Count:5 Percentile:35.08(Optics)

We have developed a 1 kHz regenerative amplifier using an Yb:Y$$_{2}$$O$$_{3}$$ ceramic thin disk as the gain medium. Furthermore, the thermal conductivity and heat generation property of Yb: Y$$_{2}$$O$$_{3}$$ 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.

JAEA Reports

Development of multi pass pumping module for thin disk laser material

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

JAEA-Technology 2015-029, 29 Pages, 2015/11

JAEA-Technology-2015-029.pdf:11.21MB

We develop high repetitive and short pulse laser system using Yb doped laser ceramics for future laser application of generating high power tera-hertz wave for experimental proof of isotope separation and generating a Laser-Compton Scattering $$gamma$$-ray source for precise specific isotopes analysis. As these future laser applications needs very stable and high average power laser system, we develop thin disk laser system using Yb:YAG ceramics because of its large stored energy property and large thermal conductivity, which could avoid thermal induced effects and thermal fracture limitation due to large pumping power. A few hundred $$mu$$m thickness of thin disk laser material in laser amplifier needs multi pass optical components for enough absorption of pump power, the pumping profile and spot size on laser disk should be variable for required laser performance. We design multi pass pumping module for thin disk laser material which consists of commercial optical components and precise stages and also design doublet and triplet for various pumping profile and spot size, the laser oscillation power is evaluated with this pumping module.

Journal Articles

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

 Times Cited Count:3 Percentile:17.23(Instruments & Instrumentation)

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$$^{2}$$. 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.

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:77.01(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

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

 Times Cited Count:7 Percentile:41.84(Materials Science, Multidisciplinary)

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 4.7$$mu$$m, 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 4$$mu$$m, 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.

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:30 Percentile:85.57(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

Picosecond view of microscopic-scale polarization clusters in paraelectric BaTiO$$_{3}$$

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

 Times Cited Count:74 Percentile:89.7(Physics, Multidisciplinary)

The polarization clusters existing in both the ferroelectric and the paraelectric phase of BaTiO$$_{3}$$ 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)$^-$0.41$$pm$$0.02 as temperature decreases toward Tc.

Journal Articles

Picosecond snapshot of the speckles from ferroelectric BaTiO$$_{3}$$ by means of X-ray lasers

Tai, R.; Namikawa, Kazumichi*; Kishimoto, Maki; Tanaka, Momoko; Sukegawa, Kota*; Hasegawa, Noboru; Kawachi, Tetsuya; Kado, Masataka; Lu, P.; Nagashima, Keisuke; et al.

Physical Review Letters, 89(25), p.257602_1 - 267602_4, 2002/12

 Times Cited Count:38 Percentile:81.07(Physics, Multidisciplinary)

no abstracts in English

Oral presentation

High resistant multilayer coatings for thin-disk laser amplifier

Ochi, Yoshihiro; Nagashima, Keisuke; Maruyama, Momoko; Okada, Hajime; Sugiyama, Akira; Tateno, Ryo*; Furukawa, Yasuyuki*

no journal, , 

We designed and fabricated high resistant AR and HR coatings using Al$$_{2}$$O$$_{3}$$ layer for Yb:YAG tin-disk amplifier. The damage threshold fluences for 520 ps pulse (AR, HR) and 1.2 ps pulse (HR only) were measured by uncompressed and compressed pulses, respectively, from the regenerative amplifier in QUADRA-T. As results, the damage threshold fluence of the AR coating of Al$$_{2}$$O$$_{3}$$/SiO$$_{2}$$ multilayer was 75 J/cm$$^{2}$$ for 520 ps pulse. This is satisfied out target value 40 J/cm$$^{2}$$ to use in the amplifiers. For the HR coating, the highest damage threshold fluences, 2.4 J/cm$$^{2}$$ for 1.2 ps pulse and 123.6 J/cm$$^{2}$$ for 520 ps pulse, respectively, were obtained by manipulating Al$$_{2}$$O$$_{3}$$/SiO$$_{2}$$ layer thickness to set a point of the maximum electric field in the SiO$$_{2}$$ layer.

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

Progress and prospects of coherent X-ray research using high power lasers in JAEA

Kawachi, Tetsuya; Nishikino, Masaharu; Sasaki, Akira; Ishino, Masahiko; Hasegawa, Noboru; Imazono, Takashi; Pikuz, T.; Faenov, A. Ya.*; Magnitskiy, S.*; Maruyama, Momoko; et al.

no journal, , 

Laser-driven X-ray sources are widely used in probing substances for new material development etc. Besides the laser-driven sources have potentials to downsizing and ultra-short duration, we carry out the coherent X-ray research, i.e., soft X-ray lasers and higher order harmonics generation (HHG) and their applications. In the source study, the first observation of X-ray mirage and HHG from relativistic plasma are presented. In the applications, we show the surface dynamics of fs laser ablation of metal observed by the X-ray interferometer. Finally we mention the prospects for the future: By the financial support from government, we started upgrade of J-KAREN laser toward PW level to realize keV coherent X-ray and high energy particle beams. By use of this high peak power laser and another high average power lasers, we will explore the possibility of ultra-short-duration short-wavelength lasers and open up new applications of high average power coherent X-rays.

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

Oral presentation

Source development and novel applications of coherent X-rays and energetic particle beams using high peak power lasers in Japan Atomic Energy Agency

Kawachi, Tetsuya; Nishikino, Masaharu; Faenov, A.*; Pikuz, T.*; Ishino, Masahiko; Hasegawa, Noboru; Magnitskiy, S.*; Pirozhkov, A. S.; Esirkepov, T. Z.; Nishiuchi, Mamiko; et al.

no journal, , 

Laser-driven particle and radiation sources have unique and attractive characteristics such as ultra-short duration, high peak brilliance and potentials of downsizing of the source etc. Recent advent of high peak power lasers toward peta-watt (PW) level makes it possible for us to realize these particle and radiation sources with higher energy region, and now we are on the stage to investigate the mechanisms in detail and to start the applications of these novel sources. In this presentation, first of all, recent research activities in major high peak power laser facilities in Japan will be introduced, and then we will present research highlights in the last few years on the source development and the applications using high peak power lasers in Japan Atomic Energy Agency (JAEA) based upon Japan-Russia collaborations.

Oral presentation

Nano-meter scale surface modifications by focused soft X-ray laser pulses

Ishino, Masahiko; Maruyama, Momoko; Hasegawa, Noboru; Nishikino, Masaharu; Tamotsu, Satoshi*; Faenov, A.*; Pikuz, T.*; Kawachi, Tetsuya; Yamagiwa, Mitsuru

no journal, , 

no abstracts in English

Oral presentation

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 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 uJ was obtained using NIR pump light of 2.7 mJ.

Oral presentation

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 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.

Oral presentation

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 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 410 nJ was obtained using NIR pump light of 2.7 mJ.

Oral presentation

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.

33 (Records 1-20 displayed on this page)