, Volume 60, Issue 2, pp 137-142

Femtosecond time-resolved reflection second-harmonic generation on polycrystalline copper

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Optical Second-Harmonic Generation (SHG) in reflection from a polycrystalline copper surface in air was studied using femtosecond time-resolved pump and probe measurements at λ=625 nm. The observed time dependence of second-harmonic yield from the probe beam demonstrates, that SHG is a very sensitive technique for measuring transient electron temperatures of metals even when these are covered by an oxide layer. For polycrystalline copper, an electron-phonon energy transfer time of 2 ps was observed, corresponding to a coupling constant of 3.75×1017 W/m3 K at average lattice temperatures of about 500 K. The analysis of experimental data indicates that the time dependence of SHG is governed by the linear dielectric function ε which, in turn, is affected by the electron temperature. There is no evidence for a temperature dependence of the nonlinear susceptibility χ(2).

Paper presented at the 129th WE-Heraeus-Seminar on “Surface Studies by Nonlinear Laser Spectroscopies”, Kassel, Germany, May 30 to June 1, 1994