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

• Published in: Optical materials 2019-02, Vol.88, p.210-217
• Main Authors: Lorrain, N., Pirasteh, P., Girault, P., Azuelos, P., Lemaître, J., Guendouz, M., Hardy, I., Thual, M., Charrier, J.
• Format: Article
• Language: English
• Subjects: Condensed Matter; Engineering Sciences; Gap reduction; Materials Science; Micro-resonator; Optics; Oxidation; Photonic; Physics; Porous silicon; Technological process
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2018.11.038

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. •Original method to obtain a low gap between the access waveguide and the racetrack cavity of a micro-resonator based on porous silica material.•Method based on a low cost standard photolithographic process.•A gap reduction of 40% of integrated porous silica micro-resonator is obtained.•The gap reduction takes benefit of the volume expansion of silicon that occurs during the full oxidation of the porous silicon micro-resonator.