High field effect on ultrafast pump–probe excitation of compound semiconductors

Abstract

The pump–probe excitation of compound semiconductors in the presence of high electric fields is studied with a model of the non-interacting photo-excited electron–hole system theoretically. Coherent excitation of the interband polarization produces an oscillatory structure in the carrier density and the differential transmission spectrum (DTS) above the band gap. The DTS profile is altered by the effect of a high electric field on both the pump excitation and the probe excitation. Our analysis reveals that the pump excitation with relatively longer pulse (100 fs ) induces the oscillatory structure in the DTS while the probe excitation with short pulse (20 fs ) gives rise to a peak shift towards the lower energy side due to the field assisted generation. The oscillation period in the DTS depends on the electric field to the two-third power, which corresponds to the Franz–Keldysh oscillation.