Thermo-optic coefficient of lithium niobate LN using optical interferometric technique

The thermo-optic coefficient is considered an important and effective factor in thermo-optic devices and in analyzing the refractive index of optical materials. The formula of the thermo-optic coefficient is considered an effective relation in thermo-optic devices because the refractive index changes with temperature at different wavelengths. In this paper, A theoretical model of the thermo-optic coefficient was designed, and the crystalline type of lithium niobate was used depending on the optical interferometric technique. The optical interferometric technique is an imperative method to analysis the thermo-optic coefficient. The Mach–Zehnder interferometer based on lithium niobate material was used for this purpose. In this work, the thermo-optical coefficient was analyzed using the thermal-optical and electro-optic effects, which doesn't appear in other formulas such as the Schott equation. The simulation result was applied using wavelengths from visible to near-infrared from 460 to 1130 nm and temperatures about 10 to 150 °C and obtained a thermo-optical coefficient less than 2.1 × 10^–6 K⁻¹ for ordinary rays and 8 × 10^–5 K⁻¹ for extraordinary ray A comparison was made between this work and other works at temperatures of 25, 85, and 150 °C. This model is considered a better performance because it uses a wide wavelength region and the widest temperature.