Approach for THz-wave difference frequency generation in surface emitting geometry

Summary form only given. Difference frequency generation (DFG) is a convenient technique to produce coherent THz radiation, although typically the efficiency of frequency conversion is low due to large damping of THz-wave in nonlinear crystal. In addition, it is impossible to increase the efficiency of THz-wave DFG by using high concentrations of laser radiation in an optical waveguide, as the thickness of optical waveguides is much less than the wavelengths of emitted wave, and therefore the output. THz-beam will have a very high divergence. These problems can be overcome by using the surface-emitting geometry. However offered earlier methods of surface-emitted THz-wave DFG are useless for organic nonlinear materials. One of best examples is 4-dimethylamino-N-methyl-4-stilbazolium-to-sylate (DAST) having both a great nonlinear coefficient and large THz-wave absorption. Recently reproducible methods for preparation of DAST optical waveguides have been established. Thus it is interesting to develop a scheme for surface-emitted DFG in DAST waveguide. In present report we offer a method of surface-emitted DFG based on the applying of metal grating (with a specific period) on the surface of a waveguide cover.