Abstract

We present measurements of spectral hole burning in room temperature GaAs. A thin (0.5-μm) GaAs sample is excited by a 60-fspulseat 618 nm (2.00 eV) and its transmission is examined using a 10-fs transform-limited probe pulse. The changes in the sample transmission are monitored in the range between 570 and 670 nm using a differential transmission technique. The sample transmission is measured in the presence and in the absence of the pump pulse, the former trace being subtracted from the latter and the result integrated. A family of these differential spectra is generated by delaying the probe with respect to the pump in 25-fs steps. The measurement is made possible due to recent improvements in femtosecond pulse amplification which allow a pulse repetition rate of 8.5 kHz. Our data show that an increase in transmission occurs selectively at the pump spectral position while the pump pulse is present. As the initial nonequilibrium population thermalizes the hole disappears. Since the pump photons have an energy of 2.00 eV, transitions from the light and heavy hole band transitions from the split off band all contribute to the observed bleaching.

© 1986 Optical Society of America