Subpicosecond spectral hole burning due to nonthermalized photoexcited carriers in GaAs.

Subpicosecond infrared pulses were used to study in GaAs at 15 K the spectral dependence of the absorption saturation around the excitation-pulse wavelength. The nonthermal part of the carrier energy distribution is found to peak at the excitation frequency. A line-shape analysis allows the determination of the electron-hole-pair dephasing time.