β-BBO, LBO, AND KTP Nonlinear Crystals as Sources of Millimeter-Wave Radiation

The refractive indices and the absorption coefficients of β-BBO, LBO, and KTP nonlinear optical crystals have been measured in the wavelength range of 0.5–3 mm at temperatures of 298 and 78 K. The absorption coefficients of all crystals at a wavelength of 1 mm do not exceed 3.5 cm –1 and fall with cooling. The anisotropy of the absorption coefficients of crystals increases significantly with decreasing wavelength (2 mm, it almost disappears. Upon cooling, the absolute values of the absorption coefficients fall below 0.2 cm –1 . Based on the measured refractive indices, the collinear phase-matching curves are simulated numerically. The theoretical feasibility of IR (1.064 μm) laser radiation conversion into the millimeter-wave range is demonstrated.