Effective Terahertz Wave Parametric Generation Depending on the Pump Pulse Width Using a LiNbO3 Crystal

Injection-seeded terahertz (THz)-wave parametric generation pumped by subnanosecond pulses was demonstrated as an exploration of the effective pump pulse width. In experiments, pump sources with different pump widths of 35-850 ps were used. The relationship between the undesirable effect of stimulated Brillouin scattering (SBS) and the THz-wave output in LiNbO
₃
was analyzed. The transient effect on SBS was not actualized around the acoustic phonon lifetime of LiNbO
₃
. Pump widths below 420 ps were found to provide THz-wave generation with an energy conversion efficiency of 10
^-4
. With a pump width of 700 ps, which is around five phonon lifetimes, the conversion efficiency was decreased about one order of magnitude from that of the pump width of 420 ps. Additionally, the peak power of the THz-wave output was maintained at about 15 kW with an actual range of 10-20 kW below 200 ps. A continuous change in the THz-wave pulse energy was obtained for six-fold energy scaling from 100 to 600 nJ.