Fast photothermal relaxation processes in metals and semiconductors studied using transient reflecting gratings

Dynamic processes forming the transient reflecting gratings are experimentally investigated in the picosecond time regime for both metals and semiconductors. The shapes of the initial parts of the grating signals were examined with respect to the pump and probe intensities, optical configurations of polarization directions and ion implantation doses. For metals, the rising part is influenced by the temperature grating independently of the corrugation grating due to surface acoustic waves. For silicon, the peak or shoulder at the initial part is attributed to the concentration grating of the photoexcited carriers, and it directly reflects the photothermal relaxation rate.