Low cost highly sensitive miniaturized refractive index sensor based on planar waveguide

A simple, compact, low cost and highly sensitive refractive index sensor based on single mode leaky planar waveguide is reported. An optical waveguide fabricated on glass substrate has been proposed to construct the sensor. In this structure Cytop works as guiding layer while Teflon forms the cladding layers. Propagation of light in Cytop layer is strongly affected by the refractive index of external medium placed on top of Teflon layer. If the refractive index of the medium is close to or greater than that of Cytop, there is leakage of power from Cytop layer to external medium which affects the transmittance of the waveguide. The structure can be designed to have strong variation in transmittance with the refractive index of external medium and, thus, can be utilized as a highly sensitive refractive index sensor for biomedical applications. In this paper we have carried out the designs of such refractive index sensor for various biological and chemical applications. We design a sensor having sensitivity of the order of 104 dB/RIU. Fabrication of the sensor can be carried out by using spin coating technique. Long sensing range, high sensitivity, simple manufacturing process and compactness make the sensor attractive for diverse applications.