Application of picosecond optical parametric amplifiers to semiconductor studies

The radiation of a picosecond parametric amplifier based on KDP crystal pumped by the second harmonic of a mode-locked Nd:YAG laser was used to investigate excitation and relaxation processes in different semiconductors on a subnanosecond time scale using time-resolved reflection, transmission, and photoconductance measurements. The excitation wavelength tunability (400-1500 nm) was used both for distinction of bulk and surface recombination and of diffusion processes in silicon and for investigation of carrier excitation processes in GaAs and CdS. Furthermore, the tunability was used to excite carriers into different states in amorphous silicon in order to separate different relaxation channels.