Submicron gap reduction of micro-resonator based on porous silica ridge waveguides manufactured by standard photolithographic process

Abstract In this paper, we demonstrate a new method to obtain a low gap between the access waveguide and the racetrack cavity of a micro-resonator based on porous silica material and using standard photolithographic process. The photolithographic process is first carried out on porous silicon layers to obtain porous silicon ridge waveguides that constitutes the racetrack micro-resonator. Then the full oxidation of the micro-resonator is performed. Because of the volume expansion of silicon that occurs during its full oxidation, the gap is reduced. Lower gaps and then lower coupling distances can be obtained using a low cost photolithographic process compared to e-beam technology. This original method proposed in this paper allows to improve the miniaturization of such porous silica micro-resonators which is of great interest for integrated optical biosensor application.