Pump-probe studies of carrier capture processes in semiconductor multiple-quantum-well waveguides

Carrier capture processes in GaAs-AlGaAs multiple-quantum-well (MQW) waveguides are monitored using the time-resolved pump-probe technique. With appropriate selections of wavelength and pulse recompression, subpicosecond pulses at various wavelengths can be obtained for both nondegenerate and degenerate pump-probe experiments with various polarization combinations. Two samples of different quantum-well structures are compared. It is found that the carrier capture times (defined as the time period to reach probe transmission maximum after the pump) are in the range from 15 to 50 ps in the samples used. In the degenerate pump-probe measurements, a two-component decay is observed for one of the samples in the case of TM pump and TE probe.