Diffractive optical waveguide and display device having the same preliminary class

A diffractive optical waveguide, comprising a waveguide substrate and a grating structure formed on a surface of the waveguide substrate, wherein,

• the grating structure comprises a plurality of grating lines arranged in a plane, the grating lines extend along a first direction in the plane and are arranged at a predetermined interval in a second direction perpendicular to the first direction;
• each of the grating lines has a first sidewall and a second sidewall, which are opposite to each other in the second direction, at least one of the first sidewall and the second sidewall has a periodic structure along the first direction, and the periodic structure makes the grating structure as a whole asymmetrical on both sides in the second direction;
• the grating structure is configured to diffract light, which is incident thereon at a non-zero angle with respect to the plane, out of the plane through a predetermined diffraction order;
• and
• the diffractive optical waveguide comprises a coupling-in grating and a coupling-out grating formed on the waveguide substrate, wherein the grating structure is configured as the coupling-in grating, and the coupling-in grating couples a light beam irradiated on the waveguide substrate at an incident angle within a predetermined range into the waveguide substrate through the diffraction of the predetermined diffraction order so that it propagates in the waveguide substrate through total reflection, the first sidewall or the second sidewall formed with the periodic structure in the coupling-in grating faces in a direction, in which light of the predetermined diffraction order propagates to the coupling-out grating, the periodic structures on the first sidewalls of different grating lines are aligned with each other in the second direction, and the coupling-out grating is configured to couple at least a portion of the light propagating from the coupling-in grating into it through total reflection out of the waveguide substrate by diffraction.