Sensitivity of grating coupled graded thin film planar waveguide sensors

摘要

The sensitivity of grating coupled planar waveguide sensors having graded film material are discussed, theoretically. The exponential and Gaussian gradation profiles are considered and conditions for high sensitivity are derived using boundary matching techniques. This type of sensor responds for change in the refractive index of the samples covering the film and formation of adlayer on the surface of waveguide film. It is observed that the graded refractive index profile in film layer highly affect the sensitivity and penetration depth of evanescent field, of a grating coupled planar waveguide based sensors. The gradation in film layer provides an extra degree of freedom to tune the sensitivity of sensors. Also, the exponential graded profile shows larger sensitivity than the Gaussian graded profile.