Diffractive optical elements with asymmetric profiles

A method of producing a molded diffractive optical element (DOE) in a waveguide-based display system, comprising:

• providing an in-coupling DOE that is configured to in-couple input images from an imager into the waveguide-based display system;
• providing an out-coupling DOE that is configured to out-couple output images from the waveguide-based display system to an eye of a user;
• providing a substrate having at least one planar surface;
• exposing the substrate to a plasma source to etch a microstructure into the planar surface in which the microstructure comprises features that are asymmetric with respect to an axis that is orthogonal to the planar surface of the substrate;
• using the etched substrate to mold a planar DOE from a polymer material in which the molded DOE includes grating features each having a slant angle to a respective axis orthogonal to the plane of the DOE;
• assembling the molded DOE into the waveguide-based display system with the in-coupling DOE and the out-coupling DOE to create a light path that sequentially traverses the in-coupling DOE, the molded DOE, and the output DOE,
• wherein at least a portion of the molded DOE includes grating features each having a slant angle to a respective axis orthogonal to the plane of the molded DOE, and
• wherein the molded DOE is configured with uniform grating features that are periodic in only a single direction.

A method for fabricating a diffractive optical element (DOE), comprising:

• providing a reactive ion etching source;
• affixing a substrate having at least one planar surface to a moveable holder;
• exposing the substrate to the reactive ion etching source to thereby etch grating features that are asymmetric with respect to an axis that is orthogonal to the planar surface;
• controlling the etching of the substrate to the reactive ion etching source by motion of the substrate relative to the reactive ion etching source;
• using the etched substrate to mold a planar DOE from a polymer material in which the molded DOE includes grating features each having a slant angle to a respective axis orthogonal to the plane of the DOE;
• and
• disposing the molded DOE on a waveguide that includes an in-coupling DOE configured as an in-coupling grating to receive one or more optical beams as an input,
• wherein the molded DOE receives the one or more optical beams from the in-coupling DOE, and
• wherein the molded DOE is configured for pupil expansion along a first direction, and
• wherein at least a portion of the molded DOE includes grating features each having a slant angle to a respective axis orthogonal to the plane of the molded DOE, and
• wherein the molded DOE is configured with uniform grating features that are periodic in only a single direction.