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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
Baba, Motoyoshi*; Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Minami, Yasuo*; Takei, Ryota*; Yamagiwa, Mitsuru; Kawachi, Tetsuya; Suemoto, Toru
Japanese Journal of Applied Physics, 53(8), p.080302_1 - 080302_4, 2014/08
Times Cited Count：7 Percentile：30.85(Physics, Applied)A grazing incidence reflection-type soft X-ay microscope, using a Fresnel zone plate and a soft X-ray laser with wavelength 13.9 nm and pulse width 7 ps, was developed. Submicron size groove structures made on a Pt film were clearly captured at a single shot exposure, with spatial resolution of about 360 nm. A wide field view of 100 
m square was secured under the Kohler illumination. This microscope also had a large depth of focus of more than 100 m and was proven to have a sufficient performance for observing surface morphological changes.
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; Baba, Motoyoshi*; Suemoto, Toru; Hasegawa, Noboru; Ishino, Masahiko; Kaihori, Takeshi; Kawachi, Tetsuya; Yamagiwa, Mitsuru
X-Ray Lasers 2012; Springer Proceedings in Physics, Vol.147, p.199 - 202, 2014/00
Times Cited Count：0 Percentile：0(Engineering, Electrical & Electronic)The dynamical processes of the laser-induced surface modifications such as laser ablation come to attract much attention for the micro processing by the ultra-short laser pulse. It is difficult to observe these phenomena directly, because they are non-repetitive, unrepeatable, and occur very rapidly (pico-second) in a very small (micron) area. In order to observe the detailed laser-ablation process, we have developed the proto-type reflected soft X-ray microscopy using the Fresnel zone plate. The experimental setup and spatial resolution of the X-ray microscopy will be presented.
Hasegawa, Noboru; Ochi, Yoshihiro; Kawachi, Tetsuya; Nishikino, Masaharu; Ishino, Masahiko; Imazono, Takashi; Kaihori, Takeshi; Morita, Toshimasa; Sasaki, Akira; Terakawa, Kota*; et al.
X-Ray Lasers 2012; Springer Proceedings in Physics, Vol.147, p.117 - 120, 2014/00
Times Cited Count：0 Percentile：0(Engineering, Electrical & Electronic)We have developed the femto-second laser pump and soft X-ray laser probe system in order to observe the dynamical processes of the femto-second laser ablation. By using this system, we succeed to obtain the temporal evolution of the soft X-ray reflectivity from the laser induced Pt surface. The results lead that the rate of decrease in the reflectivity of the probe beam has a non-linear relation with the pump laser fluence.
Nishikino, Masaharu; Hasegawa, Noboru; Ishino, Masahiko; Yamagiwa, Mitsuru; Kawachi, Tetsuya; Minami, Yasuo*; Terakawa, Kota*; Takei, Ryota*; Baba, Motoyoshi*; Suemoto, Toru; et al.
JAEA-Conf 2013-001, p.16 - 19, 2013/09
The dynamics of the femtosecond laser ablation is still not clear at the early stage. Several studies on the time-resolved imaging of femtosecond laser ablation process have been performed on various materials. In this study, we have demonstrated a pump and probe imaging of the metal surface morphology during the femtosecond laser ablation by using the laser-driven plasma induced soft X-ray laser (SXRL) as a probe beam. The pumping laser used for ablation was a Ti:Sapphire laser system based on chirped pulse amplification. The pump beam had a Gaussian profile and the focal spot size on the metal surface was about 70 micron at FWHM. The dependence for the pump laser fluence of the ablation surface expansion and the surface condition (roughness and density gradient) were observed from the soft X-ray interferogram and reflective image, respectively.
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.
Hasegawa, Noboru; Kawachi, Tetsuya; Nishikino, Masaharu; Ochi, Yoshihiro; Terakawa, Kota*; Takei, Ryota*; Minami, Yasuo*; Baba, Motoyoshi*; Suemoto, Toru; Yamagiwa, Mitsuru
no journal, ,
We developed the soft X-ray laser interferometer synchronized with Ti:Sapphire laser pulse for the measurement of the nanometer-scaled surface dynamics. The soft X-ray laser is suitable for probing the initial process of the surface morphological changes, because it has the suitable wavelength (= 13.9 nm), short duration (= 7 ps) and large photon numbers. By using this system, we succeed to obtain the temporal evolution of ablation front erupting from the laser induced Pt film. From this result, it was revealed that the expansion speed of the ablation front decreased continually from the center (= 2200 m/s) to the edge (= 420 m/s) of the ablation area in the initial stage of the ablation process.
Hasegawa, Noboru; Nishikino, Masaharu; Yamagiwa, Mitsuru; Kawachi, Tetsuya; Suemoto, Toru; Tomita, Takuro*; Baba, Motoyoshi*; Terakawa, Kota*; Minami, Yasuo*; Takei, Ryota*
no journal, ,
The dynamical processes of the laser-induced surface modifications such as laser ablation come to attract much attention for the micro processing by the ultra-short laser pulse. The soft X-ray laser (SXRL) is suitable for probing the initial process of the surface morphological changes, because it has the suitable wavelength (= 13.9 nm, penetration depth = 5 nm), short duration (= 7 ps) and large photon numbers (larger than 1e+10 photons/shot). In this study, we have developed the femto-second laser pump and soft X-ray laser probe system with the soft X-ray interferometer in order to observe the dynamical processes of the femto-second laser ablation. By using this system, we succeed to obtain the temporal evolution of the laser induced Pt surface. From this result, it was revealed that the expansion speed of the ablation front at the center (= 1500 m/s) of the ablation area in the initial stage of the ablation process.
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Takei, Ryota*; Baba, Motoyoshi*; Kawachi, Tetsuya; Yamagiwa, Mitsuru; Suemoto, Toru
no journal, ,
no abstracts in English
Nishikino, Masaharu; Hasegawa, Noboru; Tomita, Takuro*; Takei, Ryota*; Baba, Motoyoshi*; Kawachi, Tetsuya; Yamagiwa, Mitsuru; Suemoto, Toru
no journal, ,
no abstracts in English
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
Hasegawa, Noboru; Nishikino, Masaharu; Yamagiwa, Mitsuru; Kawachi, Tetsuya; Suemoto, Toru; Tomita, Takuro*; Takei, Ryota*; Baba, Motoyoshi*
no journal, ,
The dynamical processes of the laser-induced surface modifications such as laser ablation come to attract much attention for the micro processing by the ultra-short laser pulse. The soft X-ray laser (SXRL) is suitable for probing the initial process of the surface morphological changes, because it has the suitable wavelength (= 13.9 nm, penetration depth = 5 nm), short duration (= 7 ps) and large photon numbers (larger than 1e+10 photons/shot). In this study, we have developed the femto-second laser pump and soft X-ray laser probe system with the soft X-ray interferometer in order to observe the dynamical processes of the femto-second laser ablation. By using this system, we measured the surface roughness and surface modifications of the laser induced metal surface. From this result, we succeeded to obtain the clear dependence for the material (Pt, Au, W) of the laser ablation dynamics.
Hasegawa, Noboru; Nishikino, Masaharu; Kaihori, Takeshi*; Hirano, Yusuke; Morita, Toshimasa; Kawachi, Tetsuya; Yamagiwa, Mitsuru; Tomita, Takuro*; Minami, Yasuo*; Terakawa, Kota*; 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*; Onishi, Naofumi*; Hatomi, Daiki*; Ito, Atsushi*; Minami, Yasuo*; Takei, Ryota*; et al.
no journal, ,
no abstracts in English
