Surface relief grating performance and cost enhancements for augmented reality applications
Aspects of the present disclosure provide a method for fabricating a grating coupler. For example, the method can include providing a substrate, forming a plurality of grating elements and a photosensitive material above the substrate, and projecting actinic radiation of varied intensities to expose different regions of the photosensitive material, causing the photosensitive material to generate a solubility-changing agent. The method can also include removing the solubility-changing agent. The actinic radiation of varied intensities can correspond to depths of grooves between the grating elements.
1 . An optical waveguide, comprising:
a waveguide substrate;
an input grating coupler configured to couple light to propagate along a total internal reflection (TIR) path in the waveguide substrate; and
an expansion grating coupler configured to expand the light that propagates in the waveguide substrate,
wherein at least one of the input grating coupler and the expansion grating coupler includes one or more variable index grating elements, and
the variable index grating elements are formed vertically on a surface of the waveguide substrate, and each of the variable index grating elements has a variable index that is decreased exponentially toward the surface of the waveguide substrate.
2 . The waveguide of claim 1 , wherein the variable index grating elements are formed vertically on a surface of the waveguide substrate.
3 . The waveguide of claim 1 , wherein the variable index grating elements are formed in a constant pitch structure.