Predicting temperature dependence of the refractive index and nonlinear optical coefficients in lithium niobate

The optical properties of lithium niobate single crystals are quantitatively calculated at different temperatures. The chemical bond method is used to predict the temperature dependence of the refractive index and nonlinear optical coefficient variations. Employing the chemical bond method, both the refractive index and nonlinear optical coefficients of lithium niobate are theoretically derived from the corresponding crystallographic structure. Calculated results show that the optical properties of lithium niobate at 1.064 μm increase remarkably with increasing temperature, this is due to a high local effect provided by temperature on the valence electrons of constituent ions of lithium niobate. The comparison of our predictions with experimental measurements in literature is discussed. The present work shows us a clear relation among the crystal structure, optical properties, and temperature in lithium niobate single crystals.