Method for fabricating grating coupler

摘要

A grating coupler is formed by growing an optical waveguide layer on a substrate by an epitaxial growing process such as a metalorganic chemical vapor deposition and a molecular beam deposition. The optical waveguide layer has a surface on which a cross-hatch pattern serving as the grating is continuously formed. The optical waveguide layer is formed with a material having a reflective index greater than a reflective index of the substrate or an atmosphere. Specifically, the substrate is formed with GaAs and the optical waveguide layer is formed with InGaAs. Further, the substrate is an on-substrate having an orientation coinciding with a [100] plane, so as to form the optical waveguide layer having continuous cross-hatch patterns on the surface thereof. The spacing between the cross-hatch patterns can be varied according to variation of a growth temperature of the optical waveguide layer.