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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.
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.
Inogamov, N. A.*; Zhakhovsky, V. V.*; Hasegawa, Noboru; Nishikino, Masaharu; Yamagiwa, Mitsuru; Ishino, Masahiko; Agranat, M. B.*; Ashitkov, S. I.*; Faenov, A. Y.*; Khokhlov, V. A.*; et al.
Applied Physics B, 119(3), p.413 - 419, 2015/06
Times Cited Count：6 Percentile：34.43(Optics)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
Tomita, Takuro*; Nishikino, Masaharu; Hasegawa, Noboru; Minami, Yasuo*; Takei, Ryota*; Baba, Motoyoshi*; Eyama, Tsuyoshi*; Takayoshi, Shodai*; Kaihori, Takeshi*; Morita, Toshimasa; et al.
Journal of Laser Micro/Nanoengineering, 9(2), p.137 - 142, 2014/06
Times Cited Count：5 Percentile：29.55(Nanoscience & Nanotechnology)Femtosecond laser ablation processes on platinum, gold, and tungsten were observed by the single shot pump and probe reflective imaging using a soft X-ray laser probe. To avoid the timing error due to the jitter, we adopted a posteriori correction technique by simultaneous measurement of timing between the pump and probe pulses for every single shot, using a soft X-ray streak camera. A clear difference was found in the temporal behavior of the dynamical response of the soft X-ray reflectivity depending on the irradiated laser fluence in these three materials. On the other hand, the narrow dark rings were found in Pt and W, while an additional bright ring was found outside the dark disk in Au. Our result gives the experimental data comparable with various numerical simulations.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Minami, Yasuo*; Takei, Ryota*; Baba, Motoyoshi*; Eyama, Tsuyoshi*; Takayoshi, Shodai*; Kawachi, Tetsuya; Hatomi, Daiki*; et al.
Proceedings of SPIE, Vol.8849, p.88490E_1 - 88490E_6, 2013/09
Times Cited Count：2 Percentile：73.12(Optics)We have developed the pump and probe interferometer and reflective imaging technique of the metal surfaces during the femtosecond laser ablation by using the laser-driven soft X-ray laser at the wavelength of 13.9 nm. The pumping laser used for ablation was a Ti: Sapphire laser pulse with the duration of 80 fs pulse at a central wavelength of 795 nm, and had a gaussian spatial profile. By using the X-ray imaging technique, the time resolved image of nano-scaled ablation dynamics of the platinum and the gold pumped by a femtosecond laser pulse was obtained.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Minami, Yasuo*; Takei, Ryota*; Ishino, Masahiko; Terakawa, Kota*; Eyama, Tsuyoshi*; Takayoshi, Shodai*; Kawachi, Tetsuya; et al.
no journal, ,
no abstracts in English
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Minami, Yasuo*; Takei, Ryota*; Baba, Motoyoshi*; Eyama, Tsuyoshi*; Takayoshi, Shodai*; Kawachi, Tetsuya; Yamagiwa, Mitsuru; et al.
no journal, ,
We have developed the pump and probe interferometer and reflective imaging technique of the metal surfaces during the femtosecond laser ablation by using the laser-driven soft X-ray laser at the wavelength of 13.9 nm. The pumping laser used for the ablation was a Ti: Sapphire laser pulse with the duration of 80 fs pulse at a central wavelength of 795 nm, and had a gaussian spatial profile. By using the X-ray imaging technique, the time resolved image of nano-scaled ablation dynamics of the platinum, the gold, the tungsten were obtained. We have compared the plasma expansion measured by the X-ray interferometer with the ablated hole measured by the atomic force microscopy, and discussed the fluence dependence of the femtosecond laser ablation.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Hatomi, Daiki*; Onishi, Naofumi*; Baba, Motoyoshi*; Kawachi, Tetsuya; Yamagiwa, Mitsuru; et al.
no journal, ,
no abstracts in English
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Hatomi, Daiki*; Onishi, Naofumi*; Ito, Atsushi*; Kawachi, Tetsuya; Yamagiwa, Mitsuru; et al.
no journal, ,
no abstracts in English
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Hatomi, Daiki*; Ito, Atsushi*; Minami, Yasuo*; Takei, Ryota*; et al.
no journal, ,
no abstracts in English
Yamagiwa, Mitsuru; Hasegawa, Noboru; Nishikino, Masaharu; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Hatomi, Daiki*; Ito, Atsushi*; Minami, Yasuo*; et al.
no journal, ,
no abstracts in English
Hasegawa, Noboru; Nishikino, Masaharu; Tomita, Takuro*; Takei, Ryota*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Hatomi, Daiki*; Onishi, Naofumi*; Baba, Motoyoshi*; Kawachi, Tetsuya; et al.
no journal, ,
We have observed the temporal evolution of the femto-second laser irradiated metal surface by using the soft X-ray laser probe at the wavelength of 13.9 nm. The initial dynamics of the fs-laser ablation is quite rapid ( a few ps) and the dynamics of the laser processing is kept for a long time. We have developed a new pump and probe system to measure these phenomena by the same set-up. By using this system, we have succeeded to obtain the temporal evolution of the ablation front exfoliated from the laser ablated gold surface.
Hasegawa, Noboru; Nishikino, Masaharu; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Hatomi, Daiki*; Onishi, Naofumi*; Ito, Atsushi*; Minami, Yasuo*; Takei, Ryota*; et al.
no journal, ,
We have observed the temporal evolution of the femto-second laser irradiated metal surface by using the soft X-ray laser probe at the wavelength of 13.9 nm. We have succeeded to obtain the temporal evolution of the ablation front from the result of the soft X-ray reflective imaging and interferogram. We will report about "the Newton's ring generated between the ablation front and the metal surface" and "the ablation front dynamics observed by the soft X-ray shadow graph".
Nishikino, Masaharu; Hasegawa, Noboru; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Tomita, Takuro*; Hatomi, Daiki*; Onishi, Naofumi*; Ito, Atsushi*; Minami, Yasuo*; Baba, Motoyoshi*; et al.
no journal, ,
The dynamical process of laser-induced surface modification such as the laser ablation comes to attract much attention for the micro processing by the ultra-short laser pulse. In order to observe the surface morphological change during the fs laser ablation process with a weakly excitation, we have developed soft X-ray interferometer and reflectometer system. Weakly excited ablation processes of the gold (Au) films are investigated by using single shot pump and probe imaging technique, using a Ti:Sapphire laser pulse with the duration of 80 fs pulse at a central wavelength of 795 nm for the pumping of ablation and the laser-driven soft X-ray laser at the wavelength of 13.9 nm for the probe. We discuss the scenario of the weakly excited femtosecond laser ablation of the gold surface. The numerical simulation study of the fs laser ablation process is underway by using a parallel molecular dynamics code.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Ito, Atsushi*; Baba, Motoyoshi*; Minami, Yasuo*; Kawachi, Tetsuya; et al.
no journal, ,
no abstracts in English
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Ito, Atsushi*; Kawachi, Tetsuya; Yamagiwa, Mitsuru; Suemoto, Toru
no journal, ,
no abstracts in English
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Eyama, Tsuyoshi*; Kakimoto, Naoya*; Onishi, Naofumi*; Ito, Atsushi*; Baba, Motoyoshi*; Minami, Yasuo*; Inogamov, N.*; et al.
no journal, ,
Femtosecond laser ablation processes on gold and tungsten were observed by the single shot pump and probe imaging using a soft X-ray laser probe. A clear difference was found in the temporal behavior of the dynamical response of the soft X-ray reflectivity depending on the irradiated laser fluence in two materials. The duration of the femtosecond laser ablation on the tungsten is shorter than the gold case and the narrow dark rings around the crater position were found in the tungsten case. Our experimental data lead to better understanding of the initial process of the laser ablation dynamics.
