7th International Conference on X-Ray Lasers

J. Phys. IV France 11 (2001) Pr2-397-Pr2-403
DOI: 10.1051/jp4:2001276

Efficient soft X-ray generation from femtosecond-laser-produced plasma and its application to time resolved spectroscopy

N. Uesugi¹, H. Nakano², T. Nishikawa² and P. Lu<sup>3

1</sup>  Tohoku Institute of Techonology, 35-1 Yagiyama Kasumicho Taihaku-ku, Sendai 982-8577, Japan
²  NTT Basic Research Laboratories, 3-1 Wakamiya, Morinosato Atsugi-shi, Kanagawa 243-0198, Japan
³  Advanced Photon Research Center, Kansai Research Establishment, Japan Atomic Research Institute, 8-1-1-2 Umemidai, Kizucho, Souraku-gun, Kyoto-fu 619-0215, Japan

Abstract
The experimental results on efficient soft x-ray generation from fs-laser-produced plasma and the application of short x-ray pulse to time-resolved spectroscopy are presented. Soft x-ray generation properties were evaluated for both flat Al targets and nanohole - alumina targets. The experimental results for flat metal targets revealed the fundamental properties of soft x-ray emission such as broadband continuum spectra and short pulse duration. By adopting nano-structured targets, a more than 30-hold enhancement of x-ray generation yield is achieved compared with that for flat targets of the same materials with a slight increase of pulse duration. The time-resolved measurement of the inner-shell absorption change of Si during the irradiation with a high-intensity fs laser pulse is achieved by using a short soft x-ray pulse as a probe pulse in pump-probe experiments for the first time. A more than 10% increase in the absorption of Si membrane at the L_n,m edge (around 100eV) was observed. The recovery time of the absorption change was measured to be about 20ps. This absorption change is assumed to be the bandgap renormarization of Si.

© EDP Sciences 2001