Narrow-Linewidth Tunable Terahertz-Wave Sources Using Nonlinear Optics

Abstract

We review methods of generation of widely tunable terahertz (THz) waves using nonlinear optical effects. Using parametric generation of MgO-doped LiNbO3 crystals pumped by a nanosecond Q-switched Nd:YAG laser, we have built widely tunable coherent THz wave sources with a simple configuration. Fourier transform limited THz wave spectrum narrowing was achieved by introducing the injection seeding method. At the same time, the THz wave output was increased hundreds of times higher than that of a conventional generator which has no injection seeder. Also, tunable THz wave generation was demonstrated by the difference frequency generation between dual signal-wave quasi-phase-matched optical parametric oscillations, using periodically poled LiNbO3 (PPLN) with a series of gratings. An organic ionic salt, 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST) was used as a nonlinear crystal. These room-temperature operated, tabletop systems promise to be new widely tunable THz wave sources suited to a variety of applications.