Abstract
Optical responses of lithium niobate (LN) crystal under high-repetition-rate sub-nanosecond laser
irradiation is experimentally studied toward high-average-power terahertz (THz)-wave generation. In
this study, we develop a high-repetition-rate master-oscillator power amplifier system that consists of a
Nd:YVO4 microchip laser and a dual-end-pumped Nd:YVO4 amplifier. By using this pump laser, we
demonstrate an injection-seeded THz-wave parametric generator (is-TPG) with 5 mol.% MgO-doped
congruent LN crystal. A pumping condition is investigated for preventing any optical damage of the
crystal by a high electrical field or by a photorefractive effect. Eventually, we identify the
photorefractive response of the crystal as a crucial parameter for efficient THz-wave generation. The
energy conversion efficiency is degenerated when the crystal is pumped by an average power density of
above 50 kW/cm2. Finally, the average THz-wave output of 30 μW was obtained at 100 kHz repetitionrate,
which is three orders higher repetition-rate than the state-of-the-art is-TPG sources.
