Abstract

Thermal modulation of the optical properties of metals is a widely used technique in studying critical points in band structure. Recently the modulation of reflectivity of copper has been used to observe nonequilibrium electron-lattice temperatures during picosecond (~5 ps FWHM) laser heating of up to a few degrees¹. Although nonequilibrium heating was demonstrated in these experiments, the time resolution was insufficient to resolve electron-phonon relaxation. In a subsequent report, the phenomenon of thermally enhanced multiphoton photoemission was used to time-resolve electron-phonon relaxation in tungsten². Results indicated that such relaxation is accomplished in a few hundred femtoseconds. We report results obtained using amplified 150-300 fs laser pulses to time-resolve electron-phonon relaxation by monitoring the laser-heating-induced modulation of the transmissivity of 200 Å copper films.

© 1986 Optical Society of America