1.2 A tunable injection-seeded terahertz-wave parametric generator using a compact, diode-pumped Nd:YAG laser

We developed a compact (30 cm × 65 cm) tunable injection-seeded terahertz-wave parametric generator (is-TPG) with a diode-pumped Nd:YAG laser that was specially designed for pumping the is-TPG. The pump laser, which produced an output energy of 11 mJ in a single Q-switched pulse with a pulse width of 6 ns, was operated with MgO:LiNbO3 crystals and a seed source for the idler wave. A narrow THz-wave linewidth of less than 33 GHz was achieved by injection seeding of the idler wave. The terahertzwave energy was increased by a factor of 3 compared to the unseeded energy. Tunability of the terahertz frequency from 1.1 to 2.3 THz was obtained by varying the seeder frequency, and the tunable is-TPG was used to measure water vapor absorption.