A mid-infrared free electron laser (MIR-FEL) (5 – 20 µm) facility (KU-FEL: Kyoto University
Free Electron Laser) was constructed to aid various energy science researchers at the Institute
of Advanced Energy, Kyoto University. In May 2008, the first power saturation at 13.2 µm was
achieved. A pilot application to evaluate selective phonon excitation processes in solid materials by
irradiating with MIR-FEL was implemented, and a preliminary experiment without FEL irradiation
was conducted. N-doped silicon carbide (SiC) was selected as a sample material due to its unique
electrical property where the lattice vibration and the electronic structure are coupled. Two peaks,
1.8 – 2.2 eV and 2.4 – 2.8 eV, which showed strong temperature dependences in both their intensities
and peak energies, were observed. These tendencies could be explained by using a donor-acceptor
pair luminescence (DAP) model with impurity and defects in the SiC sample. The results imply
that we can verify selective phonon excitation by investigating the change in the PL spectrum
introduced by MIR-FEL irradiation.