Integrated-optic temperature sensors based on guided-mode radiation in polymer waveguide

Optical temperature sensors consisting of low-loss polymer waveguides with a glass lower cladding are demonstrated. The refractive index of the optical polymer is precisely controlled to have a certain initial refractive index contrast with the glass substrate used for lower cladding. Depending on the initial index contrast, the operating temperature ranges of the sensors are determined. The polymer devices are fabricated by spin-coating and UV curing, which could be replaced by the cost-effective imprinting or injection molding process. The sensor exhibits a monotonic decrease of the transmission intensity corresponding to the temperature increase, which enables straightforward reading of temperature from the measured optical power.