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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.
Tai, R.; Namikawa, Kazumichi; Sawada, Akikatsu*; Kishimoto, Maki; Tanaka, Momoko; Lu, P.*; Nagashima, Keisuke; Maruyama, Hiroshi*; Ando, Masami*
Physical Review Letters, 93(8), p.087601_1 - 087601_4, 2004/08
Times Cited Count：76 Percentile：89.47(Physics, Multidisciplinary)The polarization clusters existing in both the ferroelectric and the paraelectric phase of BaTiO are directly observed and characterized for the first time by a picosecond soft X-ray laser speckle technique. These dynamic clusters appear continuously across the Curie temperature Tc. The clusters' distance increases approximately linearly with temperature, while their mean size does not change significantly. The polarization exhibits a maximum at a temperature about 5 degree above Tc. The clusters' short-range correlation strength diverges as (T-Tc)
0.41
0.02 as temperature decreases toward Tc.
Hasegawa, Noboru; Nishikino, Masaharu; Kawachi, Tetsuya; Yamagiwa, Mitsuru; Tomita, Takuro*; Suemoto, Toru; Onishi, Naofumi*; Ito, Atsushi*; Baba, Motoyoshi*; Minami, Yasuo*
no journal, ,
We have succeeded in simultaneous observation of temporal evolution of two different surfaces of the femto-second laser ablation process of metals (Au) by using the soft X-ray laser probe. The ablation front with a solid or the liquid surface and the expansion front with thin film structure were observed from the results of the soft X-ray interferogram, reflective imaging and shadowgraph. The expansion front separated from the ablation front was thin, dense and smooth so as to work as the beam splitter for the soft X-rays at the time within 1 ns after the laser irradiation. The expansion front that included almost all of the mass of the crater inside was kept at the time around 1 microsecond, and the height of that reached over 100 micron. From these results, the ablation front gradually becomes vapor while maintaining a clear and smooth expansion front.
