Disclosed herein is a method for fabricating an optical device that includes depositing an etch stop material to form an etch stop layer, wherein the etch stop material has a refractive index in the infrared wavelength range, n1; depositing a core material to form a core layer, wherein the core material has a refractive index in the infrared wavelength range, n2; and etching the core layer using a halide based etch process, wherein the etch stop material has an etch rate in the halide based etch process and the core material has an etch rate in the halide based etch process, wherein the etch rate of the core material is at least about five times higher than the etch rate of the etch stop material, and wherein n1 is not greater than n2.