US Patent 11662584 Gradient refractive index grating for display leakage reduction

A waveguide display includes a waveguide, an input coupler configured to couple display light into the waveguide, and a surface-relief grating on the waveguide and configured to couple the display light out of the waveguide towards an eyebox of the waveguide display on a first side of the waveguide. The surface-relief grating is formed in a plurality of grating layers having uniform or non-uniform thickness profiles. The plurality of grating layers is characterized by a refractive index modulation that increases and then decreases as the distance of the grating layer from the waveguide increases.