SUPERIMPOSED DIFFRACTIVE GRATINGS FOR OPTICAL ELEMENTS OF AUGMENTED REALITY AND VIRTUAL REALITY DISPLAYS

Head-mounted displays with waveguides comprising superimposed diffractive gratings and methods for fabricating said waveguides are described herein. In an embodiment, a head-mounted display comprises an optical element and an image source that provides an image beam to an optical element. The optical element comprises two gratings superimposed over each other, at least one of which comprising a buried diffractive grating. The buried diffractive grating comprises a high-refractive index material interspersed with a low-refractive index material or non-solid pockets, such as gas, air or vacuum. Light diffracted by a first of the two gratings is further diffracted by a second of the two gratings without interacting with a surface of the optical element between diffractions.