Abstract

Intense ultrafast optical excitation creates unique non-equilibrium conditions in a semiconductor, strongly modifies the bandstructure, and drives structural changes.^1-3 Our previous results have shown that measuring fundamental optical properties, such as the dielectric constant¹ and second-order susceptibility² is a tremendous improvement over ordinary reflectivity and second-harmonic measurements, and yields results qualitatively different from previous assumptions. We now move beyond single-frequency measurements using a new broadband spectroscopic technique to simultaneously monitor the response of the dielectric function ε(ω) of GaAs across the spectral range from 1.5 to 3.5 eV, with 100-fs temporal resolution.

© 1996 Optical Society of America