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Kawabori, Tatsuru*; Watanabe, Masashi; Imai, Yoshiyuki; Ueta, Shohei; Yan, X.; Mizoshiri, Mizue*
Applied Physics A, 129(7), p.498_1 - 498_9, 2023/07
Times Cited Count：0 Percentile：0(Materials Science, Multidisciplinary)We investigated a potential of femtosecond laser sintering of silicon carbide (SiC) using the nanoparticles in air. A SiC nanoparticle ink including polyvinylpyrrolidone and ethylene glycol exhibited intense absorption by SiC nanoparticles at the wavelength of 780 nm. The whole of the sintered film patterns from the surface to the bottom underwent significant oxidation at a scanning speed of 1 mm/s, suggesting that the excessive energy irradiation generated silicon oxides. In contrast, the patterns fabricated by laser scanning at a raster pitch of 30 
m at which a sintered area was observed at a scanning speed of 5 mm/s, exhibited no significant difference in oxidation of the raw SiC nanoparticles except for the surfaces from 1.72 m. These results indicate that the irradiation of femtosecond laser pulses generated the sintered SiC patterns without additional atmospheric oxidation of the raw materials because of its low heat accumulation. In additions, the dispersant of polyvinylpyrrolidone and ethylene glycol did not affect the sintering by an X-ray photoelectron spectroscopy. This vacuum-free direct printing technique has the potential for additive manufacturing.
Wada, Yoriko*; Akagi, Hiroshi*; Kumada, Takayuki; Itakura, Ryuji*; Wakabayashi, Tomonari*
Photochem (Internet), 2(3), p.798 - 809, 2022/09
Coulomb explosion experiments using 60 fs laser pulses were conducted for structural characterization of three dichloroethylene isomers. Under laser intensity at 1.8 
10
W/cm
, mass-resolved momentum imaging (MRMI) for selected fragment ions of 
Cl
and C
revealed different patterns for the three isomers. The C
ion fragmented from multiply charged trans-1,2-DCE was forced to leave perpendicularly to the direction of the laser polarization, due to recoil forces from adjacent cations. In contrast, the fast ions of C from cis-1,2-DCE exhibited an isotropic distribution, whereas the fast ions of C from 1,1-DCE recoiled along the laser polarization together with the slow C ions, and thereby distinction of the three isomers was demonstrated. Coulomb explosion occurs predominantly at specific orientation, which is useful for potential applications of MRMI analysis to molecular structure assays.
Kumada, Takayuki
Purazuma, Kaku Yugo Gakkai-Shi, 96(4), p.176 - 180, 2020/04
We have developed time-resolved reflectivity measurement system using femtosecond laser pulses, which can measure structure of thin films generated by non-thermal effect.
Kumada, Takayuki; Otobe, Tomohito; Nishikino, Masaharu; Hasegawa, Noboru; Hayashi, Terutake*
Applied Physics Letters, 108(1), p.011102_1 - 011102_4, 2016/01
Times Cited Count：12 Percentile：49.85(Physics, Applied)The dynamics of photomechanical spallation during femtosecond laser ablation of fused silica was studied by time-resolved reflectivity with double pump pulses. Oscillation of reflectivity was caused by interference between the probe pulses reflected at the sample surface and the spallation layer, and was enhanced when the surface is irradiated with the second pump pulse within a time interval of several picoseconds after the first pump pulse. However, as the time-interval was increased, the oscillation amplitude decreased with an exponential decay time of 10 ps. The oscillation disappeared when the interval exceeded 20 ps. This result suggests that the formation time of the spallation layer is approximately 10 ps.
Hasegawa, Noboru; Nishikino, Masaharu; Tomita, Takuro*; Onishi, Naofumi*; Ito, Atsushi*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Izutsu, Rui*; Minami, Yasuo*; Baba, Motoyoshi*; et al.
X-Ray Lasers and Coherent X-Ray Sources; Development and Applications XI (Proceedings of SPIE, Vol.9589), p.95890A_1 - 95890A_8, 2015/09
Times Cited Count：1 Percentile：55.52(Optics)We have improved a soft X-ray laser (SXRL) interferometer synchronized with a Ti:Sapphire laser pulse to observe the single-shot imaging of the nano-scaled structure dynamics of the laser induced materials. By the precise imaging optics and double time fiducial system having been installed, the lateral resolution on the sample surface and the precision of the temporal synchronization between the SXRL and Ti:Sapphire laser pulses were improved to be 700 nm and 2 ps, respectively. By using this system, the initial stage (before 200 ps) of the ablation process of the Pt surface pumped by 80 fs Ti:Sapphire laser pulse was observed by the comparison between the soft X-ray reflective image and interferogram. We have succeeded in the direct observation of the unique ablation process around the ablation threshold such as the rapid increase of the surface roughness and surface vibration.
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(Optics)Hasegawa, Noboru; Tomita, Takuro*; Nishikino, Masaharu; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Minami, Yasuo*; Baba, Motoyoshi*; Onishi, Naofumi*; Ito, Atsushi*; Kawachi, Tetsuya; et al.
JAEA-Conf 2015-001, p.17 - 20, 2015/07
We have succeeded in simultaneous observation of the ablation front and the expansion front with thin filmy structure in the femto-second laser ablation process of a gold target by using the 13.9 nm soft X-ray probe (incident angle to the sample 
70 deg) with soft X-ray interferometer. The dependence on the laser local fluence and materials was obtained by the comparison between gold and tungsten.
Kumada, Takayuki; Akagi, Hiroshi; Itakura, Ryuji; Otobe, Tomohito; Nishikino, Masaharu; Yokoyama, Atsushi
Applied Physics Letters, 106(22), p.221605_1 - 221605_5, 2015/06
Times Cited Count：3 Percentile：13.89(Physics, Applied)The dynamics of femtosecond laser ablation of transparent polymers were examined using time-resolved reflectivity. When these polymers were irradiated by a pump pulse with fluence above the ablation threshold of 0.8-2.0 J/cm
, we observed the oscillation of the reflectivity caused by the interference between the reflected probe pulses from the sample surface and the thin layer due to the non-thermal photomechanical effects of spallation. As the fluence of the pump pulse increased, the separation velocity of the thin layer increased from 6 km/s to an asymptotic value of 11 km/s. It is suggested that the velocities are determined by shock-wave velocities of the photo-excited layer.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Ito, Atsushi*; Baba, Motoyoshi*; Minami, Yasuo*; Kawachi, Tetsuya; et al.
Reza Gakkai Dai-471-Kai Kenkyukai Hokoku; Tanhacho Ryoshi Bimu Hassei To Sono Oyo, p.9 - 12, 2014/12
no abstracts in English
Uesaka, Mitsuru*; Iijima, Hokuto; Ueda, Toru*; Muroya, Yusa*; Sakumi, Akira*; Kumagai, Noritaka*; Tomizawa, Hiromitsu*
Proceedings of 1st Annual Meeting of Particle Accelerator Society of Japan and 29th Linear Accelerator Meeting in Japan, p.628 - 630, 2004/08
no abstracts in English
Nishioka, Hajime*; Kawanaka, Junji
Hikari Araiansu, 14(11), p.21 - 25, 2003/11
no abstracts in English
Kawanaka, Junji; Yamakawa, Koichi; Nishioka, Hajime*; Ueda, Kenichi*
Optics Letters, 28(21), p.2121 - 2123, 2003/11
Times Cited Count：86 Percentile：93.68(Optics)no abstracts in English
Nishiuchi, Mamiko; Daido, Hiroyuki; Takabe, Hideaki*; Matsukado, Koji*
Reza Kenkyu, 31(11), p.711 - 720, 2003/11
no abstracts in English
Aoyama, Makoto; Harimoto, Tetsuo*; Ma, J.; Akahane, Yutaka; Yamakawa, Koichi
Optics Express (Internet), 9(11), p.579 - 585, 2001/11
Times Cited Count：22 Percentile：70.19(Optics)no abstracts in English
Aoyama, Makoto*; Zhang, T.*; Tsukakoshi, Motoo*; Yamakawa, Koichi
Japanese Journal of Applied Physics, Part 1, 39(6A), p.3394 - 3399, 2000/06
Times Cited Count：7 Percentile：35.15(Physics, Applied)no abstracts in English
Aoyama, Makoto; Zhang, T.*; Tsukakoshi, Motoo*; Yamakawa, Koichi
Japanese Journal of Applied Physics, 39(5A-Pt.1), p.2651 - 2652, 2000/05
Times Cited Count：2 Percentile：12.63(Physics, Applied)no abstracts in English
Kando, Masaki; Ahn, H.; Dewa, Hidenori; Kotaki, Hideyuki; Ueda, Toru*; Uesaka, Mitsuru*; Watanabe, Takahiro*; Nakanishi, Hiroshi*; Ogata, Atsushi*; Nakajima, Kazuhisa
Japanese Journal of Applied Physics, Part 2, 38(8B), p.L967 - L969, 1999/08
Times Cited Count：23 Percentile：69.06(Physics, Applied)no abstracts in English
Kumada, Takayuki; Akagi, Hiroshi; Itakura, Ryuji; Otobe, Tomohito; Yokoyama, Atsushi
no journal, ,
We observed oscillation of time-resolved reflectivity of femtosecond-laser-ablated fused silica. We ascribe the oscillation to the interference between probe pulses reflected from a sample surface and a thin layer produced by the photomechanical effect.
Kumada, Takayuki; Akagi, Hiroshi; Itakura, Ryuji; Otobe, Tomohito; Yokoyama, Atsushi
no journal, ,
We observed oscillation of time-resolved reflectivity of femtosecond-laser-ablated polymers. We ascribe the oscillation to the interference between probe pulses reflected from a sample surface and a thin layer produced by the photomechanical effect.
Nakashima, Nobuaki*; Yamanaka, Kenichi*; Yatsuhashi, Tomoyuki*; Taniguchi, Seiji*; Saeki, Morihisa; Oba, Hironori
no journal, ,
no abstracts in English
