Characterization of sol-gel derived grating couplers for sensing application

In this work, grating couplers fabricated by sol-gel technique are studied for sensing application. Assuming that the measurand is the refractive index of a film acting as a cover layer, the expression for homogeneous sensitivity, defined as the change of effective refractive index of the guiding mode to the change in cover layer refractive index, is first derived using the basic grating coupler theory. Next the dependence of homogeneous sensitivity and waveguiding condition on grating thickness and period respectively for different grating materials are studied. Thereafter, several characterizations of the fabricated grating couplers are done and the waveguiding characteristics of the fabricated couplers are analyzed based on the developed theory. Finally, the sensing property of the fabricated coupler is also established.