Application of a two-wavelength picosecond laser to semiconductors

We report a two-wavelength (each of which is independently tunable) synchronously pumped picosecond laser which has large spectral separation, high conversion efficiency, and wide tuning ranges. The laser has been used to find the time-resolved reflectivity of a photoexcited semiconductor in the bandgap region. Unusually rapid relaxation of the screened excitonic reflectivity has been noted and a simple carrier diffusion model is proposed. The model also predicts results which agree with previously published data.