Input/output coupling grating and display including the same

A head-mounted display system comprising:

• a head-mountable frame;
• a light projection system configured to output light to provide image content;
• a waveguide supported by the head-mountable frame, the waveguide configured to guide at least a portion of the light from the light projection system coupled into the waveguide;
• a grating structure optically coupled to the waveguide, the grating structure being configured to couple the light from the light projection system into the waveguide, the grating structure comprising:
• a grating layer comprising a grating comprising a plurality of ridges having a blaze profile in at least one cross-section, the blaze profile comprising an anti-blaze angle of 89° or less;
• and
• one or more additional layers disposed on the grating layer, the one or more additional layers comprising a first layer of a material having a refractive index of 1.5 or less at an operative wavelength of the head-mounted display system, the first layer being an outermost layer of the grating structure,
• wherein the grating layer is disposed between the waveguide and the one or more additional layers, and the first layer is discontinuous between adjacent ridges of the plurality of ridges.