Planar optical waveguides for sensing applications

Planar optical waveguides formed by ion-exchange in glass are sensitive to changes in parameters such as: refractive index, absorption, and light-emitting processes such as chemiluminescence or fluorescence. Parameter changes will cause modulation of light travelling within glass waveguides, and may be useful for optical sensors in industrial and clinical applications. Deposition of metal and dielectric layers allows the design of ‘all optical’ device structures which must be capable of surviving harsh working conditions for both civilian and military applications. A planar optical waveguide is shown to exhibit a rapid response of only a few seconds to ultraviolet (UV) radiation at 6 mW cm−2. A prototype waveguide sensor is demonstrated for refractive index measurement. Preliminary results for the detection of gaseous chemical species, such as ammonia, via pH-driven optical changes, for possible use in an aqueous environment are given. The presence of both guided modes and sensitive surface modes may lead to further expansion in waveguide sensors, telecommunications and signal processing applications.