Frequency-tunable terahertz wave generation via excitation of phonon-polaritons in GaP and beam properties

High-power, frequency-tunable terahertz (THz) waves over the range from 0.3 to 7.5 THz were generated based on difference-frequency generation in GaP crystals using a YAG laser and an optical parametric oscillator. The THz-wave linewidth was estimated to 3.2 GHz and spatial distribution is discussed. We measured the absorption coefficient of the GaP as well as spectra of polytetrafluroethylene (PTFE) in the THz frequency region.