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Journal Articles

Soft X-ray laser observation of femtosecond-laser-driven ablation of tungsten

Nishikino, Masaharu; Hasegawa, Noboru; Ishino, Masahiko; Ochi, Yoshihiro; Kawachi, Tetsuya; Yamagiwa, Mitsuru; Kato, Yoshiaki*

Chinese Optics Letters, 13(7), p.070002_1 - 070002_3, 2015/07

 Times Cited Count:1 Percentile:7.36(Optics)

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:33 Percentile:85.9(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

Terahertz tomography of a photo-induced carrier based on pump-probe spectroscopy using counterpropagation geometry

Tsubouchi, Masaaki; Nagai, Masaya*; Oshima, Yasuhiro*

Optics Letters, 37(17), p.3528 - 3530, 2012/09

 Times Cited Count:17 Percentile:64.52(Optics)

A novel technique for the terahertz (THz) tomography of a photo-induced carrier that is based on optical-pump THz-probe time-resolved reflection spectroscopy using counter-propagation geometry of the pump and probe pulses has been proposed. Transient reflection due to the photo-induced carrier provides information about the physical properties and spatial distribution separately. We have experimentally demonstrated this method using a silicon wafer. The obtained complex reflection can be reproduced by the exact solution of Maxwell's equations, assuming an exponential distribution of the photo-induced carrier density.

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:38 Percentile:86.33(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

Proton acceleration to 40 MeV using a high intensity, high contrast optical parametric chirped-pulse amplification/Ti:sapphire hybrid laser system

Ogura, Koichi; Nishiuchi, Mamiko; Pirozhkov, A. S.; Tanimoto, Tsuyoshi*; Sagisaka, Akito*; Esirkepov, T. Z.; Kando, Masaki; Shizuma, Toshiyuki; Hayakawa, Takehito; Kiriyama, Hiromitsu; et al.

Optics Letters, 37(14), p.2868 - 2870, 2012/07

 Times Cited Count:81 Percentile:96.11(Optics)

Using high contrast (10$$^{10}$$:1) and high intensity (10$$^{21}$$ W/cm$$^{2}$$) laser pulse with the duration of 40 fs from OPCPA/Ti:Sapphire laser, a 40 MeV proton bunch is obtained, which is a record for laser pulse with energy less than 10 J. The efficiency for generation of protons with kinetic energy above 15 MeV is 0.1%.

Journal Articles

Generation of hard X rays by femtosecond laser pulse interaction with solid targets in atmosphere

Zhidkov, A. G.*; Pikuz, S. A.*; Faenov, A. Y.; Chefonov, O. V.*; Ovchinikov, A. V.*; Agranat, M. B.*; Zigler, A.*

Optics Letters, 37(5), p.884 - 886, 2012/03

 Times Cited Count:3 Percentile:18.61(Optics)

Journal Articles

Efficient generation of Xe K-shell X rays by high-contrast interaction with submicrometer clusters

Hayashi, Yukio; Pirozhkov, A. S.; Kando, Masaki; Fukuda, Yuji; Faenov, A.*; Kawase, Keigo*; Pikuz, T.*; Nakamura, Tatsufumi; Kiriyama, Hiromitsu; Okada, Hajime; et al.

Optics Letters, 36(9), p.1614 - 1616, 2011/05

 Times Cited Count:22 Percentile:72.26(Optics)

The interaction between a 25 TW laser and Xe clusters at a peak intensity of 1$$times$$10$$^{19}$$ W/cm$$^2$$ has been investigated. Xe K-shell X-rays, whose energies are approximately 30 keV, were clearly observed with a hard X-ray charge-coupled device (X-ray CCD) at 3.4 MPa. Moreover, we studied the yield of the Xe K-shell X-rays by changing the pulse duration of the laser at a constant laser energy, and found that the pulse duration of 40 fs is better than that of 300 fs for generating Xe K-shell X-rays.

Journal Articles

Laser ceramic materials for subpicosecond solid-state lasers using Nd$$^{3+}$$ -doped mixed scandium garnets

Okada, Hajime; Tanaka, Momoko; Kiriyama, Hiromitsu; Nakai, Yoshiki*; Ochi, Yoshihiro; Sugiyama, Akira; Daido, Hiroyuki; Kimura, Toyoaki*; Yanagitani, Takagimi*; Yagi, Hideki*; et al.

Optics Letters, 35(18), p.3048 - 3050, 2010/09

 Times Cited Count:13 Percentile:54.86(Optics)

Journal Articles

High temporal and spatial quality petawatt-class Ti:sapphire chirped-pulse amplification laser system

Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya; Sasao, Hajime; Tanoue, Manabu*; Kanazawa, Shuhei; Wakai, Daisuke*; Sasao, Fumitaka*; Okada, Hajime; et al.

Optics Letters, 35(10), p.1497 - 1499, 2010/05

 Times Cited Count:85 Percentile:95.5(Optics)

OPCPA (Optical parametric chirped-pulse amplification) operation with low gain by seeding with high energy, clean pulses is shown to significantly improve the contrast to better than $$10^{-10}$$-$$10^{-11}$$ in a high intensity Ti:sapphire laser system that is based on chirped pulse amplification. In addition to the high contrast broadband high energy output from the final amplifier is achieved with a flat-topped spatial profile of filling factor near 77%. This is the result of pump beam spatial profile homogenization with diffractive optical elements. Final pulse energies exceed 30-Joules indicating capability for reaching peak powers in excess of 500-TW.

Journal Articles

Observation of a plasma waveguide in a preformed plasma pumped by double-pulse laser irradiation for the efficient soft X-ray amplification

Kawachi, Tetsuya; Hasegawa, Noboru; Nishikino, Masaharu; Ochi, Yoshihiro; Sasaki, Akira

Optics Letters, 34(5), p.635 - 637, 2009/03

 Times Cited Count:0 Percentile:0(Optics)

A molybdenum slab target was irradiated by double pulses of line-focused CPA Nd:glass laser. A probe beam was injected in the plasma in the longitudinal direction, and we found that the probe beam was guided in the plasma with the plasma length of up to 4.3 mm at the time of 0.8 $$sim$$ 1.5 ns after the peak of the second pulse. Comparison with hydrodynamics code implied that the electron density dip or flat region was formed, which was favorable for the efficient soft X-ray lasing under the coupling of seed X-ray and X-ray amplifier.

Journal Articles

Split-aperture laser pulse compressor design tolerant to alignment and line-density differences

Rushford, M. C.*; Britten, J.*; Barty, C. P. J.*; Jitsuno, Takahisa*; Kondo, Kiminori; Miyanaga, Noriaki*; Tanaka, Kazuo*; Kodama, Ryosuke*; Xu, G.*

Optics Letters, 33(16), p.1902 - 1904, 2008/08

 Times Cited Count:14 Percentile:57.31(Optics)

We introduce a four-pass laser pulse compressor design based on two grating apertures with two gratings per aperture that is tolerant to some alignment errors and, importantly, to grating-to-grating period variations. Each half-beam samples each grating in a diamond-shaped compressor that is symmetric about a central bisecting plane. For any given grating, the two half-beams impinge on opposite sides of its surface normal. It is shown that the two split beams have no pointing difference from paired gratings with different periods. Furthermore, no phase shift between half-beams is incurred as long as the planes containing a grating line and the surface normal for each grating of the pair are parallel. For grating pairs satisfying this condition, gratings surfaces need not be on the same plane, as changes in the gap between the two can compensate to bring the beams back in phase.

Journal Articles

High-contrast, high-intensity laser pulse generation using a nonlinear preamplifier in a Ti:sapphire laser system

Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Shimomura, Takuya*; Tanoue, Manabu*; Akutsu, Atsushi; Kondo, Shuji; Kanazawa, Shuhei; Okada, Hajime; Motomura, Tomohiro*; et al.

Optics Letters, 33(7), p.645 - 647, 2008/04

 Times Cited Count:70 Percentile:93.7(Optics)

We report on a high-contrast, high-intensity Ti:sapphire chirped-pulse amplification system that incorporates a nonlinear pre-amplifier based on optical parametric chirped-pulse amplification (OPCPA) for use in experiments where relativistic effects dominate the physics. By cooling the Ti:sapphire crystal in the final amplifier down to 77 K, the chirped-pulses are amplified to 2.9 J at 10 Hz repetition rate without thermal lensing effect. Pulse compression down to 19-fs duration obtained after amplification indicates a peak power of 80 TW. With the OPCPA, the temporal contrast is significantly improved to better than 7$$times$$10$$^{-9}$$ in a few picoseconds interval prior to the main laser pulse.

Journal Articles

High-energy diode-pumped picosecond regenerative amplification at 999 nm in wavelength with a cryogenically cooled Yb:LuLiF$$_{4}$$ crystal

Akahane, Yutaka; Aoyama, Makoto; Sugiyama, Akira; Kubo, Ryoichi; Ogawa, Kanade; Tsuji, Koichi; Yamakawa, Koichi

Optics Letters, 33(5), p.494 - 496, 2008/03

 Times Cited Count:2 Percentile:14.93(Optics)

A diode-pumped, cryogenically-cooled Yb:LuLiF$$_{4}$$ regenerative amplifier has been developed for the first time to our knowledge. A chirped-seed pulse was amplified and compressed in the regenerative amplifier, simultaneously, which generated $$sim$$6-mJ, 13-ps pulses at 999 nm wavelength without a pulse compressor. Simultaneous lasing at 999 nm and 1024 nm, respectively, was demonstrated, which could be used for different frequency generation in the THz region.

Journal Articles

Elemental sensitivity in soft X-ray imaging with a laser-plasma source and a color center detector

Calegari, F.*; Valentini, G.*; Vozzi, C.*; Benedetti, E.*; Cabanillas-Gonzalez, J.*; Faenov, A. Y.; Gasilov, S.*; Pikuz, T.*; Poletto, L.*; Sansone, G.*; et al.

Optics Letters, 32(17), p.2593 - 2595, 2007/09

 Times Cited Count:25 Percentile:73.55(Optics)

Journal Articles

High-energy, high-contrast, multiterawatt laser pulses by optical parametric chirped-pulse amplification

Kiriyama, Hiromitsu; Mori, Michiaki; Nakai, Yoshiki; Yamamoto, Yoichi*; Tanoue, Manabu*; Akutsu, Atsushi; Shimomura, Takuya*; Kondo, Shuji; Kanazawa, Shuhei; Daido, Hiroyuki; et al.

Optics Letters, 32(16), p.2315 - 2317, 2007/08

 Times Cited Count:49 Percentile:87.68(Optics)

We describe a compact, reliable, high-power, and high-contrast noncollinear optical parametric chirped-pulse amplifier system. With a broadband Ti:sapphire oscillator and grating-based stretching and compression, the chirped pulses are amplified from 0.1 nJ to 122 mJ in type-I $$beta$$-barium borate optical parametric chirped pulse amplifiers with a total gain of over 10$$^{9}$$ at 10 Hz repetition rate. Pulse compression down to 19-fs duration achieved after amplification indicates a peak power of 3.2 TW at an average power of 0.62 W. The pre-pulse contrast is measured to be less than 10$$^{-8}$$ on picosecond timescales.

Journal Articles

High-energy, diode-pumped, picosecond Yb:YAG chirped-pulse regenerative amplifier for pumping optical parametric chirped-pulse amplification

Akahane, Yutaka; Aoyama, Makoto; Ogawa, Kanade; Tsuji, Koichi; Tokita, Shigeki*; Kawanaka, Junji*; Nishioka, Hajime*; Yamakawa, Koichi

Optics Letters, 32(13), p.1899 - 1901, 2007/07

 Times Cited Count:40 Percentile:84.37(Optics)

A diode-pumped, cryogenic-cooled Yb:YAG regenerative amplifier utilizing gain-narrowing has been developed. A 1.2-ns chirped-seed pulse was amplified and compressed in the regenerative amplifier, simultaneously, which generated a 35-ps pulse with $$sim$$8-mJ of energy without a pulse compressor. Second-harmonics of the amplified pulse was used to pump picosecond two-color optical parametric amplification.

Journal Articles

Elongation of plasma channel for electron acceleration

Chen, L.-M.; Nakajima, Kazuhisa; Hong, W.*; Hua, J. F.*; Kameshima, Takashi; Kotaki, Hideyuki; Sugiyama, Kiyohiro*; Wen, X.*; Wu, Y.*; Tang, C.*; et al.

Chinese Optics Letters, 5(S1), p.S133 - S135, 2007/05

Journal Articles

Two-color chirped-pulse amplification in an ultrabroadband Ti:sapphire ring regenerative amplifier

Yamakawa, Koichi; Barty, C. P. J.*

Optics Letters, 28(23), p.2402 - 2404, 2003/12

 Times Cited Count:32 Percentile:76.59(Optics)

no abstracts in English

Journal Articles

30-mJ, diode-pumped, chirped-pulse Yb:YLF regenerative amplifier

Kawanaka, Junji; Yamakawa, Koichi; Nishioka, Hajime*; Ueda, Kenichi*

Optics Letters, 28(21), p.2121 - 2123, 2003/11

 Times Cited Count:86 Percentile:93.89(Optics)

no abstracts in English

Journal Articles

X-ray laser beam with diffraction-limited divergence generated with two gain media

Tanaka, Momoko; Nishikino, Masaharu; Kawachi, Tetsuya; Hasegawa, Noboru; Kado, Masataka; Kishimoto, Maki; Nagashima, Keisuke; Kato, Yoshiaki

Optics Letters, 28(18), p.1680 - 1682, 2003/09

 Times Cited Count:64 Percentile:90.45(Optics)

We have demonstrated an x-ray laser at a wavelength of 13.9 nm with a beam divergence of 0.2 mrad, which is 1.8 times the diffraction limit. The x-ray laser is generated using two gain media, where the seed x-ray pulse from the first medium is amplified in the second medium. The effect of refraction on x-ray propagation is reduced by spatially and temporally controlling the injection of the seed x-ray to the second medium.

29 (Records 1-20 displayed on this page)