Effects of electron relaxation on multiple harmonic generation from metal surfaces with femtosecond laser pulses
| Autor: | N. E. Karatzas, A. T. Georges |
|---|---|
| Rok vydání: | 2006 |
| Předmět: |
Materials science
business.industry Autocorrelator Second-harmonic generation Laser Atomic and Molecular Physics and Optics Electronic Optical and Magnetic Materials law.invention Optics law Ultrafast laser spectroscopy Femtosecond Harmonic High harmonic generation Electrical and Electronic Engineering Physical and Theoretical Chemistry business Ultrashort pulse |
| Zdroj: | Optics Communications. 267:498-504 |
| ISSN: | 0030-4018 |
| DOI: | 10.1016/j.optcom.2006.06.058 |
| Popis: | Calculations are presented for the first four (odd and even) harmonics of an 800 nm laser from a gold surface, with pulse widths ranging from 100 down to 14 fs. For peak laser intensities above 1 GW/cm 2 the harmonics are enhanced because of a partial depletion of the initial electron states. At 10 11 W/cm 2 of peak laser intensity the calculated conversion efficiency for 2nd-harmonic generation is 3 × 10 −9 , while for the 5th-harmonic it is 10 −10 . The generated harmonic pulses are broadened and delayed relative to the laser pulse because of the finite relaxation times of the excited electronic states. The finite electron relaxation times cause also the broadening of the autocorrelations of the laser pulses obtained from surface harmonic generation by two time-delayed identical pulses. Comparison with recent experimental results shows that the response time of an autocorrelator using nonlinear optical processes in a gold surface is shorter than the electron relaxation times. This seems to indicate that for laser pulses shorter than ∼30 fs, the fast nonresonant channel for multiphoton excitation via continuum-continuum transitions in metals becomes important as the resonant channel becomes slow (relative to the laser pulse) and less efficient. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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