Temperature dependence of refractive indices for 4H- and 6H-SiC

Abstract

The refractive indices of 4H- and 6H-SiC single crystals at wavelengths of 404.7, 435.8, 480.0, 546.1, 587.5, 643.8, 706.5, 852.1, 1014.0, 1529.6, and 2325.4 nm are carefully measured from 293 to 493 K by the method of minimum deviation. We find that ordinary (no) and extraordinary (ne) refractive indices for both crystals increase with the elevated temperature. The temperature-dependent Sellmeier equations of refractive indices for 4H- and 6H-SiC are obtained and then thermo-optic coefficients (TOCs) are derived. The TOCs diminish very quickly at visible light region and become less dependent in the infrared light region. Such changing trends of TOCs can be explained by single-oscillator approximation. The results may provide the important reference value for designing the optoelectronic and nonlinear optical devices based on SiC.