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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:5 Percentile:50.18(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:2 Percentile:71.88(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

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:13 Percentile:20.67(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

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:18 Percentile:16.52(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

High power laser developments with femtosecond to nanosecond pulse durations for laser shock science and engineering

Kiriyama, Hiromitsu; Mori, Michiaki; Suzuki, Masayuki*; Daito, Izuru*; Okada, Hajime; Ochi, Yoshihiro; Tanaka, Momoko; Sato, Masatoshi*; Tamaoki, Yoshinori*; Yoshii, Takehiro*; et al.

Reza Kenkyu, 42(6), p.441 - 447, 2014/06

We describe three specific high power laser systems that are being developed in our laboratory for many applications in high field science, nonlinear optics and material processing. We report on a femtosecond petawatt-class Ti:sapphire chirped-pulse amplification laser system that can produce a pulse energy of 20 J of 40 fs pulse duration, a picosecond high intensity Yb:YAG chirped-pulse amplification laser system that can generate a pulse energy of 100 mJ of 0.5 ps pulse duration, and a nanosecond high repetition rate Nd:YAG laser system that can provide an average power of 360 W with a pulse duration of 30 ns delivered at a 1 kHz repetition rate. We discuss the basic design aspects and present the results from our experimental investigations of these laser systems.

Journal Articles

Polarization-selectable cavity locking method for generation of laser Compton scattered $$gamma$$-rays

Kosuge, Atsushi; Mori, Michiaki; Okada, Hajime; Hajima, Ryoichi; Nagashima, Keisuke

Optics Express (Internet), 22(6), p.6613 - 6619, 2014/03

 Times Cited Count:2 Percentile:79.6(Optics)

Nowadays, generation of energy-tunable, monochromatic $$gamma$$-rays is needed to establish a nondestructive assay method of nuclear fuel materials. The $$gamma$$-rays are generated by collision of laser photons stored in a cavity and relativistic electrons. We propose a configuration of an enhancement cavity capable of performing polarization control fabricated by a combination of a four-mirror ring cavity with a small spot inside a cavity and a three-mirror of reflective optics as an image inverter for polarization-selectable $$gamma$$-rays. The image inverter introduces a phase shift of specific polarization which can be used to generate an error signal to lock an optical cavity at a resonance condition.

Journal Articles

Development of high resistant anti-reflection coating by using Al$$_{2}$$O$$_{3}$$/SiO$$_{2}$$ multilayer

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

Proceedings of SPIE, Vol.8885, p.88851Z_1 - 88851Z_6, 2013/11

 Times Cited Count:4 Percentile:6.33

We designed and fabricated high damage-resistant AR coating using Al$$_{2}$$O$$_{3}$$/SiO$$_{2}$$ layers. As a result of irradiation test using 500 ps pulses at 1 kHz, the damage threshold of the AR coating was estimated to be over 36 J/cm$$^{2}$$ (average value). We also fabricated high reflection (HR) mirrors using Al$$_{2}$$O$$_{3}$$/SiO$$_{2}$$ layers added on Ta$$_{2}$$O$$_{5}$$/SiO$$_{2}$$ layers and measured damage threshold of them for 7 ns, 500 ps, and 1 ps pulses.

Journal Articles

Improvement of diffraction efficiency of dielectric transmission gratings using anti-reflection coatings

Nagashima, Keisuke; Kosuge, Atsushi; Ochi, Yoshihiro; Tanaka, Momoko

Optics Express (Internet), 21(16), p.18640 - 18645, 2013/07

 Times Cited Count:10 Percentile:41.13(Optics)

A novel method for increasing diffraction efficiency of transmission gratings is proposed. In this method, dielectric multilayers are inserted between a grating region and a substrate. These multilayers work as an anti-reflection coating for the transmission grating. It is presented that a grating with 1740 grooves/mm has the diffraction efficiency over 99% using this anti-reflection coating.

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:84.58(Materials Science, Multidisciplinary)

Journal Articles

Ultra-intense, high spatio-temporal quality petawatt-class laser system and applications

Kiriyama, Hiromitsu; Shimomura, Takuya; Mori, Michiaki; Nakai, Yoshiki*; Tanoue, Manabu; Kondo, Shuji; Kanazawa, Shuhei; Pirozhkov, A. S.; Esirkepov, T. Z.; Hayashi, Yukio; et al.

Applied Sciences (Internet), 3(1), p.214 - 250, 2013/03

 Times Cited Count:11 Percentile:69.38(Chemistry, Multidisciplinary)

This paper reviews techniques for improving the temporal contrast and spatial beam quality in an ultra-intense laser system that is based on chirped-pulse amplification (CPA). We describe the design, performance, and characterization of our laser system, which has the potential for achieving a peak power of 600 TW. We also describe applications of the laser system in the relativistically dominant regime of laser-matter interactions and discuss a compact, high efficiency diode-pumped laser system.

Journal Articles

Negative effect of crystallization on the mechanism of laser damage in a HfO$$_{2}$$/SiO$$_{2}$$ multilayer

Tateno, Ryo*; Okada, Hajime; Otobe, Tomohito; Kawase, Keigo*; Koga, J. K.; Kosuge, Atsushi; Nagashima, Keisuke; Sugiyama, Akira; Kashiwagi, Kunihiro*

Journal of Applied Physics, 112(12), p.123103_1 - 123103_3, 2012/12

 Times Cited Count:2 Percentile:87.32(Physics, Applied)

Elucidation of the mechanisms of laser damage is indispensable in realizing high resistance mirrors for the next generation of ultra-short pulse high intensity lasers. In this study, the surface and a section of the laser-damaged area of a laser mirror were observed with a laser microscope and a transmission electron microscope (cross-sectional TEM), respectively. A grain boundary of HfO$$_{2}$$ microcrystal was observed in the damaged area. This observation, and an evaluation of the mirror's damage resistance showed that the formation of crystals in the multilayer mirror is one of the major determinants of damage resistance.

Journal Articles

Erratum; Design of rectangular transmission gratings fabricated in LiNbO$$_{3}$$ for high-power terahertz-wave generation [Jpn. J. Appl. Phys. 49 (2010) 122504]

Nagashima, Keisuke; Kosuge, Atsushi

Japanese Journal of Applied Physics, 51(11), P. 119201_1, 2012/11

 Times Cited Count:4 Percentile:8.21(Physics, Applied)

Erratum; Design of rectangular transmission gratings fabricated in LiNbO$$_{3}$$ for high-power terahertz-wave generation [Jpn. J. Appl. Phys. 49 (2010) 122504]

Journal Articles

Temporal contrast enhancement of petawatt-class laser pulses

Kiriyama, Hiromitsu; Shimomura, Takuya; Sasao, Hajime; Nakai, Yoshiki*; Tanoue, Manabu; Kondo, Shuji; Kanazawa, Shuhei; Pirozhkov, A. S.; Mori, Michiaki; Fukuda, Yuji; et al.

Optics Letters, 37(16), p.3363 - 3365, 2012/08

 Times Cited Count:29 Percentile:11.89(Optics)

We demonstrate the temporal contrast enhancement in a petawatt-class Ti:sapphire chirped-pulse amplification (CPA) laser system. An extra saturable absorber, introduced downstream a low gain optical parametric chirped-pulse amplification (OPCPA) preamplifier, has improved the temporal contrast in the system to 1.4$$times$$10$$^{12}$$ on the sub-nanosecond time scale at 70 TW power level. We have achieved 28 J of uncompressed broadband output energy with this system, indicating the potential for reaching peak powers near 600 TW.

Journal Articles

Development of a compact high-spatiotemporal-quality Yb:YAG thin-disk laser system using an optical parametric preamplifier

Kiriyama, Hiromitsu; Suzuki, Masayuki*; Daito, Izuru; Okada, Hajime; Ochi, Yoshihiro; Sato, Masatoshi*; Tamaoki, Yoshinori*; Yoshii, Takehiro*; Maeda, Junya*; Matsuoka, Shinichi*; et al.

Reza Kenkyu, 40(2), p.143 - 145, 2012/02

We demonstrate a compact, high-spatiotemporal-quality, high-intensity diode-pumped Yb:YAG thin-disk chirped-pulse amplification (CPA) laser system that incorporates a nonlinear preamplifier based on optical parametric chirped-pulse amplification (OPCPA). The stretched pulses are amplified in the OPCPA preamplifier and the following Yb:YAG main amplifier to $$sim$$100 mJ at 10 Hz. The broadband amplified beam quality of 1.1 (horizontal direction) and 1.4 (vertical direction) times diffraction limited and pulse compression down to 470 fs with contrast of better than 10$$^{-8}$$ have been achieved successfully.

Journal Articles

Development of silver tape target system for high repetition X-ray laser

Nishikino, Masaharu; Ochi, Yoshihiro; Hasegawa, Noboru; Kawachi, Tetsuya; Oba, Toshiyuki; Kaihori, Takeshi; Nagashima, Keisuke

X-Ray Lasers 2010; Springer Proceedings in Physics, Vol.136, p.93 - 98, 2011/12

The improvement of X-ray laser generation so as to have a high repetition rate will open up the possibility of new applications. In the last decade, progress in reducing the required pump energy for the X-ray lasing and raising the repetition rate has been achieved by new technologies, such as the Transient Collisional Excitation (TCE) scheme and Grazing Incidence Pumping (GRIP). Under this circumstance, the development of continuous pumping to the target system is an important issue for realizing an XRL with the high repetition rate. We have developed a 13.9 nm XRL using a silver tape target4 and demonstrated a highly coherent XRL with an oscillator-amplifier configuration5 using two tape target systems and the TOPAZ laser system6 with a 10-J and a 0.1-Hz repetition rate. The output energy is comparable to the X-ray laser generated with a silver-deposited slab target, and the pointing stability using the new tape target system is better than conventional slab target.

Journal Articles

Condition of MeV electron bunch generated from Argon gas-jet target in the self-modulated laser wakefield regime

Mori, Michiaki; Kando, Masaki; Kotaki, Hideyuki; Hayashi, Yukio; Bulanov, S. V.; Koga, J. K.; Kondo, Kiminori; Pirozhkov, A. S.; Nishimura, Hiroaki*; Nagashima, Keisuke

Journal of the Physical Society of Japan, 80(10), p.105001_1 - 105001_2, 2011/09

 Times Cited Count:2 Percentile:75.59(Physics, Multidisciplinary)

The effects of plasma density and laser power on the energetic electron bunch generation in an Argon (high-Z) gas-jet target in the self modulated laser wakefield acceleration regime were investigated. A vector potential threshold for electron injection was obtained $$a_{rm th}$$ $$sim$$ 2.8 through a simple analytical model include two-dimensional laser pulse compression by relativistic self-focusing, and it is similar to that after accounting for three-dimensional laser pulse compression in the standard Laser Wakefield acceleration regime.

Journal Articles

Design of rectangular transmission gratings fabricated in LiNbO$$_{3}$$ for high-power terahertz-wave generation

Nagashima, Keisuke; Kosuge, Atsushi

Japanese Journal of Applied Physics, 49(12), p.122504_1 - 122504_4, 2010/12

 Times Cited Count:16 Percentile:36.28(Physics, Applied)

Precise parameters are investigated for rectangular transmission gratings fabricated in LiNbO$$_{3}$$ substrate for the purpose of high-power terahertz-wave generation. Here, a simple setup is considered, where the pumping laser is injected to the grating surface from air or fused silica. The maximum diffraction efficiencies are 0.4 for air and 0.9 for fused silica. The designed gratings have deep grooves with the depth of about 0.5 $$mu$$m and the width of 0.12-0.14 $$mu$$m. It was found that the diffraction efficiency is much less sensitive to the groove depth, than to the groove width.

Journal Articles

Demonstration of submicroJoule, spatially coherent soft-X-ray laser pumped by 0.1 Hertz, 10 Joule, picosecond laser

Ochi, Yoshihiro; Kawachi, Tetsuya; Hasegawa, Noboru; Nishikino, Masaharu; Oba, Toshiyuki; Tanaka, Momoko; Kishimoto, Maki; Kaihori, Takeshi; Nagashima, Keisuke; Sugiyama, Akira

Japanese Journal of Applied Physics, 48(12), p.120212_1 - 120212_3, 2009/12

 Times Cited Count:26 Percentile:23.89(Physics, Applied)

We have demonstrated the fully spatial coherent 13.9-nm laser with output energy of submicroJoule by means of the double target geometry by using new driver system. The power amplifiers providing tow beams with 10-J energy and picoseconds duration at the repetition rate of 0.1 Hz. The obtained 13.9-nm laser pulse with 10$$^{10}$$ coherent photons will enable us to make single-shot pump-probe observation of non-periodic ultrafast phenomena.

243 (Records 1-20 displayed on this page)