OPTICAL LAYERS TO IMPROVE PERFORMANCE OF EYEPIECES FOR USE WITH VIRTUAL AND AUGMENTED REALITY DISPLAY SYSTEMS

1 . An eyepiece for an XR display system, comprising:

a diffractive optical element (DOE) to receive light associated with one or more frames of image data and direct the light to a user's eyes, the DOE comprising a diffraction structure having a waveguide substrate having a first side and a second side opposing the first side, a surface grating positioned on a first side of the waveguide substrate, and one or more optical layer pairs disposed between the waveguide substrate and the surface grating; and

each optical layer pair comprising a low index layer and a high index layer disposed directly on an exterior side of the low index layer, wherein the high index layer has a higher refractive index than the low index layer.

2 . The eyepiece of claim 1 , wherein the one or more optical layer pair(s) are disposed directly on first side of the waveguide substrate.

3 . The eyepiece of claim 1 , further comprising one or more intermediate layers disposed between the optical layer pair(s) and the waveguide substrate.

4 . The eyepiece of claim 1 , where the one or more optical layer pairs comprises:

a first optical layer pair on the first side of the waveguide substrate; and

a second optical layer pair on the second side of the waveguide substrate.

5 . The eyepiece of claim 1 , further comprising:

a second surface grating on the second side of the waveguide substrate, wherein the second optical layer pair is between the waveguide substrate and the second surface grating.

6 . The eyepiece of claim 1 , further comprising:

an input coupling grating disposed on the first side of the waveguide substrate; and

a first reflector disposed on the second side of the waveguide substrate.

7 . The eyepiece of claim 1 , wherein the waveguide substrate has a refractive index higher than the refractive index of the low index layer.

8 . The eyepiece of claim 1 , wherein:

the high index layer is comprised of a material selected from the group consisting of Si 3 N 4 , ZrO 2 , TiO 2 , SiC, ZnTe, GP, and BP, and the high index layer has a refractive index of greater than about 1.7; and

the low index layer is comprised of a material selected from the group consisting of MgF, SiO 2 , a UV curable resin, and a thermal curable resins, and the low index layer has a refractive index of less than about 1.53.

9 . The eyepiece of claim 1 , wherein the grating surface(s) have a lower refractive index than the high index layer.

10 . The eyepiece of claim 1 , further comprising:

a top surface layer disposed on an exterior surface of the surface grating, the top surface layer having a refractive index higher than the refractive index of the low index layer.

11 . An extended reality (XR) display system for delivering extended reality content to a user, comprising:

an image-generating source to provide one or more frames of image data;

a light modulator to transmit light associated with the one or more frames of image data; and

a diffractive optical element (DOE) to receive light associated with one or more frames of image data and direct the light to a user's eyes, the DOE comprising a diffraction structure having a waveguide substrate having a first side and a second side opposing the first side, a surface grating positioned on a first side of the waveguide substrate, and one or more optical layer pairs disposed between the waveguide substrate and the surface grating; and

each optical layer pair comprising a low index layer and a high index layer disposed directly on an exterior side of the low index layer, wherein the high index layer has a higher refractive index than the low index layer.

12 . The system of claim 11 , wherein the one or more optical layer pair(s) are disposed directly on first side of the waveguide substrate.

13 . The system of claim 11 , wherein the diffraction structure further comprises one or more intermediate layers disposed between the optical layer pair(s) and the waveguide substrate.

14 . The system of claim 11 , where the one or more optical layer pairs comprises:

a first optical layer pair on the first side of the waveguide substrate; and

a second optical layer pair on the second side of the waveguide substrate.

15 . The system of claim 11 , wherein the diffraction structure further comprises:

a second surface grating on the second side of the waveguide substrate, wherein the second optical layer pair is between the waveguide substrate and the second surface grating.

16 . The system of claim 11 , further comprising:

an input coupling grating disposed on the first side of the waveguide substrate; and

a first reflector disposed on the second side of the waveguide substrate.

17 . The system of claim 11 , wherein the waveguide substrate has a refractive index higher than the refractive index of the low index layer.

18 . The system of claim 11 , wherein:

the high index layer is comprised of a material selected from the group consisting of Si 3 N 4 , ZrO 2 , TiO 2 , SiC, ZnTe, GP, and BP, and the high index layer has a refractive index of greater than about 1.7; and

the low index layer is comprised of a material selected from the group consisting of MgF, SiO 2 , a UV curable resin, and a thermal curable resins, and the low index layer has a refractive index of less than about 1.53.

19 . The system of claim 11 , wherein the grating surface(s) have a lower refractive index than the high index layer.

20 . The system of claim 11 , wherein the diffraction structure further comprises:

a top surface layer disposed on an exterior surface of the surface grating, the top surface layer having a refractive index higher than the refractive index of the low index layer.

21 . (canceled)