Temperature-dependent dispersion relations for RbTiOPO₄ and RbTiOAsO₄

We have measured the first and second derivatives of the refractive index with respect to temperature along the z- and y-axes for two nonlinear optical materials, RbTiOPC₄ and RbTiOAsO₄. The measurements were done using an interferometric setup in the wavelength range of 532-1580 nm and in the temperature range of 25-200°C. In addition, the thermal expansion coefficients were measured in the x direction. Experimental results of nonlinear frequency conversion in RbTiOAsO₄ were used to explore the temperature dependence of the refractive index in the z-axis near 3.5 microns. We have derived thermal-dependent dispersion equations for the two materials. Calculations based on these dispersion equations are in good agreement with previously reported measurements. The thermal dependence of the refractive index of RbTiOAsO₄ is greater than that of RbTiOPO₄ by approximately 15% and 70% in the z- and y-axes, respectively. Hence RbTiOPO ₄ is more appropriate for applications that require immunity to thermal lensing, whereas RbTiOAsO₄ is suitable for realizing temperature-tuned nonlinear devices.