High-Brightness and Continuously Tunable Terahertz-Wave Generation

One of the interesting frequency regions lies in the “frequency gap” region between millimeter wave and infrared, terahertz (THz) wave. Although new methods for generating terahertz radiation have been developed, most sources cannot generate high-brightness (high-peak-power and narrow-linewidth) and continuously tunable terahertz waves. Here, we introduce the generation of high-brightness and continuously tunable terahertz waves using parametric wavelength conversion in a nonlinear crystal; this is brighter than many specialized sources such as far-infrared free-electron lasers. We revealed novel optical parametric wavelength conversion using stimulated Raman scattering in lithium niobate as a nonlinear crystal without stimulated Brillouin scattering using recently developed microchip Nd:YAG laser. Furthermore, we show how to optimize the tuning curve by controlling the pumping and seeding beam. These are very promising for extending applied research into the terahertz region, and we expect that this source will open up new research fields such as nonlinear optics in the terahertz regio