Measurement of the refractive-index variations with temperature of hybrid sol–gel glasses

Abstract

We report the measurement of variation in refractive index vs. temperature for organic–inorganic slab waveguides. The following parameters have been obtained: refractive index n; thermo-optic constant d n/d T; and linear thermal expansion coefficient. The refractive index has been measured between approximately 10 and 80 °C. For both polarization TE (Transverse Electric) and TM (Transverse Magnetic), the slopes (d n/d T) are linear over the temperature range with a correlation coefficient r≥0.997 at a wavelength of 632.8 nm. Using the prism coupling method we verified that the refractive index variations follow the Lorentz–Lorenz law. A zero-birefringence is obtained. The thermo-optic coefficient for different slab waveguides was found to be almost constant and not exceeding 10 −4/°C.