Optical eyepiece using single-sided patterning of grating couplers

1. An eyepiece comprising:

a substrate;

an in-coupling grating patterned on a single side of the substrate;

a first grating coupler patterned on the single side of the substrate and having a first grating pattern, wherein:

the first grating coupler is optically coupled to the in-coupling grating,

the first grating coupler comprises a plurality of protrusions, each protrusion of the plurality of protrusions having one or more sidewalls and at least two intersecting ridges oriented in two different directions,

an angle between the two different directions is in a range from 55 degrees to 65 degrees, and

each sidewall of the one or more sidewalls is oriented at a different angle to the substrate; and

a second grating coupler patterned on the single side of the substrate and adjacent to the first grating coupler, the second grating coupler having a second grating pattern different from the first grating pattern, wherein the second grating coupler is optically coupled to the in-coupling grating.

2. The eyepiece of claim 1 , wherein each protrusion of the plurality of protrusions has at least one of a cylindrical shape, an ellipsoidal shape, at least one rectangular surface, at least one circular surface, at least one triangular surface, or has at least one polygonal surface.

3. The eyepiece of claim 1 , wherein a fill factor of a volume of each protrusion of the plurality of protrusions measured along a direction of light incident on the plurality of protrusions from the in-coupling grating is in a range from 10% and 90%.

4. The eyepiece of claim 1 , wherein a pitch of an axis of the plurality of protrusions is in a range from 300 nm to 450 nm.

5. The eyepiece of claim 1 , wherein a diagonal pitch of the plurality of protrusions is in a range from 300 nm to 900 nm.

6. The eyepiece of claim 1 , wherein a height of each protrusion of the plurality of protrusions is in a range from 5 nm to 500 nm.

7. The eyepiece of claim 1 , wherein at least one of a width or a length of each protrusion of the plurality of protrusions is in a range from 5 nm to 800 nm.

8. The eyepiece of claim 1 , wherein a cross-section of each protrusion of the plurality of protrusions has at least one of a triangular shape, a sawtooth shape, or a staircase shape.

9. The eyepiece of claim 1 , wherein each protrusion of the plurality of protrusions comprises a plurality of cuboids, and wherein each cuboid of the plurality of cuboids has a different height.

10. The eyepiece of claim 1 , wherein the first grating coupler comprises a plurality of recesses, each recess of the plurality of recesses having one or more sidewalls, and wherein each sidewall of the one or more sidewalls is oriented at a different angle to the substrate.

11. A The method for manufacturing an eyepiece, the method comprising:

providing a substrate;

patterning an in-coupling grating on a single side of the substrate;

patterning a first grating coupler on the single side of the substrate, the first grating coupler optically coupled to the in-coupling grating and having a first grating pattern, wherein the patterning of the first grating coupler comprises:

patterning a plurality of protrusions on the single side of the substrate, each protrusion of the plurality of protrusions having one or more sidewalls, and wherein each sidewall of the one or more sidewalls is oriented at a different angle to the substrate; and

patterning at least two intersecting ridges oriented in two different directions for each protrusion of the plurality of protrusions, wherein an angle between the two different directions is in a range from 55 degrees to 65 degrees; and

patterning a second grating coupler on the single side of the substrate and adjacent to the first grating coupler, wherein the second grating coupler is optically coupled to the in-coupling grating and has a second grating pattern different from the first grating pattern.