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Optics

1999

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Probing Nonequilibrium Electron Distributions In Gold By Use Of Second Harmonic Generation, K. L. Moore '99, Thomas D. Donnelly Jul 1999

Probing Nonequilibrium Electron Distributions In Gold By Use Of Second Harmonic Generation, K. L. Moore '99, Thomas D. Donnelly

All HMC Faculty Publications and Research

Second-harmonic radiation is generated at a gold surface by use of a laser pulse that is varied in duration from 14 to 29 fs and in intensity from 109 to 1011W/cm2 . At laser intensities below 1010W/cm2 , the second-harmonic signal has the expected quadratic dependence on pump-laser intensity; however, at higher intensities, the dependence is supraquadratic. This difference arises because the leading edge of the laser pulse interacts significantly with the gold electrons to create a nonequilibrium, photoexcited distribution. The second-harmonic generation process occurs before electron–electron or electron–phonon collisions can ...