Temperature dependence of pyrolysed sol-gel planar waveguide parameters

A set-up for varying the temperature (5-90 degrees C) of planar optical waveguides useful in sensing applications is described. The principle is to control the temperature of the cover medium (in this case water). The propagation constants of guided modes are measured via a grating coupler. Only that part of the waveguide in the immediate vicinity of the incoming external light beam is heated or cooled. The temperature coefficients of the thickness and refractive index of the waveguide material can be described by simple polynomial expressions.