Band-gap dynamics and nonlinear propagation of optical pulses in CdTe

Abstract

The nonlinear propagation of picosecond pulses in CdTe is investigated. First, the band-gap dynamics is studied in the presence of a dense electron-hole plasma using time-resolved luminescence in the picosecond regime. Good agreement is found between experimental results for band-gap shrinkage and theory for densities of 5×1016–4×1017 cm−3. Second, the nonlinear transmission of optical pulses through CdTe/CdZn0.04Te0.96 heterostructures is investigated for photon energies close to the unexcited band gap. We demonstrate that, depending on the energy of the incident pulse, induced transmission or induced absorption takes place: Self-induced transmission is caused by band filling at high intensity E of the incident pulses (E≂100–200 μJ/cm2). Self-induced absorption is observed at relatively low incident intensity (E≂15–20 μJ/cm2). This effect is related to the band-gap shrinkage of the CdTe epilayer in the presence of a nondegenerate electron-hole plasma. A transmission theory of picosecond pulses propagating in and exciting the sample simultaneously is developed and provides a qualitative description of the experimental data.