Observation of mode-selective phonon excitation of 6H-SiC by MIR-FEL pump and pico-second probe laser

Mode-selective phonon excitation induced by MIR-FEL laser irradiation on a bulk 6H-SiC has been investigated by anti-Stokes (AS) Raman scattering spectroscopy using pico-second laser. We observed a clear peak at 965 cm −1 which corresponds to the absorption energy of the lattice vibration of 6H-SiC when the pump laser wavelength was 10.4 μm (962 cm −1 ). However, two peaks were observed by slightly detuned pump laser wavelength. Results of time resolved measurement suggested that the origin of these peaks were AS Raman scattering and sum frequency generation on 6H-SiC sample.