Rubidium titanyl arsenate difference-frequency generation and validation of new Sellmeier coefficients

Rubidium titanyl arsenate (RTA), a crystallographic isomorph of potassium titanyl phosphate, shows promise for nonlinear-frequency generation throughout the 1-5-mu m spectral region. Difference-frequency generation in an RTA crystal produced tunable output in the 3.2-4.2-mu m wavelength range. A single 1.064-mu m Nd:YAG laser pumped both a LiNbO3 optical parametric oscillator used to generate a tunable signal beam and the RTA crystal used for difference-frequency generation. Conversion efficiencies were limited to 4% primarily by the large beam divergence of the signal beam. Phase-matching measurements were in excellent agreement with new IR-corrected RTA Sellmeier equations based on refractive-index measurements. (C) 1996 Optical Society of America.