Growth and optical properties of nonlinear optical crystal Rb4Li2TiOGe4O12

Rb4Li2TiOGe4O12 (RLTG) crystals were grown with excess Rb2CO3 and LiF by the top-seeded solution growth (TSSG) method. Several attempts of growth at different cooling rates were carried out and a crystal with better quality and dimensions of 39 × 38 × 23 mm3 was obtained at the lowest cooling rate. The transmission spectra of crystal plates with various thicknesses show that the transmittance in the infrared (IR) above 3.5 μm decreases as crystal thickness increases, but the crystal plate with thickness of 10.47 mm still shows adequate transmittance in this range. The refractive indices of the crystal were measured in the wavelength range of 0.363–1.014 μm, and the Sellmeier equations were obtained by fitting the measured refractive indices. The derived result shows that the crystal may have the possibility of phase matching in the mid-IR range.