Above bandgap thermo-optic coefficient measurements for direct bandgap materials.

摘要

Accurate values of the optical functions of gallium arsenide in the very near infrared region are particularly important for many technological applications. Many different techniques have been used to measure the thermo-optic coefficients, most of which require ad hoc samples, such as those based on prism-shaped specimens or on diffraction grating photonic devices. For bulk crystals, the two-channel spectroscopic polarization modulation ellipsometer has been shown to be quite accurate in the determination of the optical functions at elevated temperatures. This work presents a simple approach to determine the thermo-optic coefficients of gallium arsenide above the bandgap for elevated temperatures. To our knowledge, these measurements have not been pursued, but they do provide important information for optical fiber communications. The method is based on the Fresnel equations, which are used to understand the interaction of light with matter. Numerical results show the method to be both stable and accurate.