Integrated optical sensor for environment monitoring

A brief overview on integrated optical sensors for environment monitoring is given. A variety of optical transducers is illustrated and the interaction between the evanescent electromagnetic field and the polluted medium under detection is described in detail. A chemically selective layer on the waveguide core binds and/or absorb the polluting molecules contained in the liquid or gaseous sample. The variation of the real and/or the imaginary part of the sensitive layer refractive index affects the penetration depth of the evanescent field of the core guided waves. Many sensor, based on this principle, configurations have been developed for chemical and biochemical applications. As an example, in this review the main numerical results pertaining to integrated optical sensors for hydrocarbon detection in water are illustrated. Various kind of planar waveguide sensors are designed by considering a polydimethylsiloxane (PDMS) polymeric overlay. The waveguide cross-section is refined to enhance the evanescent optical field, which interacts with the surrounding polymeric overlay and effects the waveguide sensor performance. The sensor based on this approach detects changes in the waveguide attenuation constant induced by the penetration of the hydrocarbons into the PDMS. The obtained results show that the proposed sensors could represent good candidates in terms of detection sensitivity and, in addition, to identify different analytes mixed in water solution