Observation of optical precursors at pulse propagation in GaAs

Abstract

We have observed optical precursors by studying propagation of ultrashort optical pulses with a steeply rising and an exponentially decaying trailing edge through a 0.2-μm-thick GaAs crystal near the exciton resonance. The appearance of a fast pulse front—the precursor—independent of the detuning with respect to the resonance, was accompanied by a delayed main pulse. The delay of the main pulse varies with detuning in according with theoretical predictions.