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Ultrashort-pulse laser ellipsometric pump-probe experiments on gold targets
Hitoki Yoneda1, Hidetoshi Morikami, Ken-ichi Ueda
1Institute for Laser Science, University of Electro-communications, Chofu, Tokyo 182-8585, Japan.
Physical Review Letters
|August 26, 2003
Summary
Ultrashort-pulse laser pump-probe ellipsometry reveals gold plasma behavior. Recombination in the expanding plasma leads to partial transparency, consistent with theoretical predictions.
Area of Science:
- Physics
- Materials Science
- Plasma Physics
Background:
- Ultrashort-pulse lasers enable probing dynamic material properties.
- Ellipsometry is a sensitive technique for characterizing thin films and surfaces.
- Laser-matter interactions create transient plasma states.
Purpose of the Study:
- To investigate the optical properties of laser-induced gold plasma.
- To analyze the dynamics of plasma expansion and transparency.
- To correlate experimental data with theoretical plasma models.
Main Methods:
- Performed ultrashort-pulse laser pump-probe ellipsometry on gold targets.
- Measured time-resolved p- and s-polarized reflectivity and the s-p phase difference.
- Analyzed data by plotting reflectivity ratios and phase differences.
Main Results:
- Experimental data followed a consistent curve across different pump intensities.
- Observed behavior consistent with a partially transparent blowoff.
- Determined atomic polarizability of the expanding plasma to be (-1.75+0.2i)x 10(-24) cm(3).
Conclusions:
- Recombination in the expanding gold plasma is responsible for its partial transparency.
- The Saha equation predicts recombination and negative ion formation.
- Maxwell's equations provide a good approximation for the observed plasma behavior.