Surface Grating Fabrication by Inductively Coupled Plasma Dry Etching for InP-Based Photonic Integrated Circuits

Surface gratings are widely used in photonic integrated circuits (PICs). In this paper, the authors study the fabrication of surface gratings on indium phosphide (InP) based materials by inductively coupled plasma (ICP) dry etching. The etching parameters are optimized to achieve high aspect ratio while maintaining excellent surface morphology. A novel processing technique is presented for surface grating formation on top of a deeply etched ridge waveguide by taking advantages of the lag effect. Fine structures with non-uniform height can be completed in a single-step ICP dry etching, thus greatly simplifying the fabrication by eliminating the demanding overlay process. The method is believe to be valuable for the fabrication of a variety of PICs containing hyperfine structures.