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Proceedings Paper

Study of optical properties of ultrashort-pulse laser-heated material
Author(s): Hitoki Yoneda; Satoru Ohta; Ken-ichi Ueda; Richard M. More
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Paper Abstract

For the purpose pf determining optical properties of high-density plasmas created by ultra-short-pulse lasers, we have measured reflectivity with the pump-probe method. Nominal parameters of pump laser were 248nm, 300fs, and 1013~1014W/cm2 and those of probe beam were 745nm and 120fs. In the case of Al target and a normal incidence probe beam, the reflectivity decreased with time after arrival of the pump pulse. The duration of this change in reflectivity was apparently longer than pulse duration of pump beam at high intensities, while it was almost the same as pulse duration of pump beam for lower irradiance. A change of absorption during the pump pulse and non-linear dependence of resistivity on temperature could not explain these observations. A simple layered structure model was proposed in which heated layer penetrates into cold region with time and interferometric reflection occurs. This model could qualitatively explain the experimental results. Ellipsometric parameters were also measure with a single-shot based four-detector system. There were different time histories observed for the ratios of I(0,0), I(π/2,0) and I(π/4, π/2). This result also implies the plasma has some layered structure.

Paper Details

Date Published: 19 February 2003
PDF: 5 pages
Proc. SPIE 4830, Third International Symposium on Laser Precision Microfabrication, (19 February 2003); doi: 10.1117/12.486507
Show Author Affiliations
Hitoki Yoneda, Univ. of Electro-communications (Japan)
Satoru Ohta, Univ. of Electro-communications (Japan)
Ken-ichi Ueda, Univ. of Electro-communications (Japan)
Richard M. More, National Institute for Fusion Science (Japan)

Published in SPIE Proceedings Vol. 4830:
Third International Symposium on Laser Precision Microfabrication
Isamu Miyamoto; Kojiro F. Kobayashi; Koji Sugioka; Reinhart Poprawe; Henry Helvajian, Editor(s)

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