Collinear injection-seeded terahertz parametric generator

Abstract

In a conventional injection-seeded terahertz (THz) parametric generator (is-TPG), a complicated achromatic optical system controlling the angle of incidence of the seed beam is used to ensure tunability because both the pump and seed beams must satisfy non-collinear phase-matching conditions. In this study, we found that a THz output and tunability similar to those characteristics of a conventional is-TPG can be obtained even when the pump and seed beams are coaxially injected into the LiNbO3 crystal. In this new generation mechanism, a weak THz-wave is generated by the difference frequency of optical mixing between the pump and seed beams at the Cherenkov phase-matching angle and then strongly parametrically amplified. Thus, we describe our device as a collinear is-TPG. Simplicity is improved by eliminating any need for achromatic optics.