ULTRAFAST DYNAMICS OF HOLES IN GAAS PROBED BY 2-COLOR FEMTOSECOND SPECTROSCOPY

Ultrafast relaxation dynamics of light and heavy holes in GaAs followi ng femtosecond valence-to-conduction-band excitation are measured by p robing the light- and heavy-to-split-off hole transitions at different midinfrared wavelengths using the recently developed broadly tunable femtosecond optical parametric oscillator. The initial relaxation time s are less than 75 fs, and a spectral hole-burning effect is seen. The results suggest that carrier-carrier and optical-phonon scattering, i n particular, polar optical-phonon scattering, are the primary process es leading to the initial redistribution of heavy and light holes. (C) 1998 American Institute of Physics.