An environmental sensor based on an integrated optical whispering gallery mode disk resonator

In this report, we describe the fabrication and testing of an integrated optical whispering gallery mode resonator designed for use as an evanescent eld environmental sensor. We use traditional photolithographic techniques to create 500 m radius disk resonators in silicon oxy-nitride. The evices are overclad with a thin film of SiO2 to provide a suitable surface for subsequent chemical adhesion of organic compounds and protein ayers. Tests performed with sucrose solutions indicate a sensitivity to surface index variations of n∼ 1.0× 10−5 refractive index units (RIU). e also demonstrate the ability of these devices to monitor protein layers binding to the surface. 2006 Published by Elsevier B.V.