Waveguides with high index materials and methods of fabrication thereof
Waveguides comprising materials with refractive index greater than or equal to 1.8 and methods of patterning waveguides are disclosed. Patterned waveguides comprising materials with refractive index greater than or equal to 1.8 can be incorporated in display devices, such as, for example wearable display devices to project virtual images to a viewer.
1. An optical device comprising:
a substrate comprising a material having a refractive index greater than 2.0 that is transparent to visible light, said substrate comprising a waveguide;
a plurality of diffractive features formed in said substrate; and
a layer of material disposed over said diffractive features,
wherein the plurality of diffractive features are asymmetrical so as to provide for a blazed grating, or wherein the plurality of diffractive features have material asymmetrically deposited thereon so as to provide for a blazed grating.
2. The optical device of claim 1 , wherein said substrate material comprises lithium niobate or silicon carbide.
3. The optical device of claim 1 , wherein said substrate material has an index of refraction that is at least 2.1.
4. The optical device of claim 1 , wherein said layer of material has an index of refraction that is less than 1.8.
5. The optical device of claim 1 , wherein said layer of material comprises photoresist.
6. The optical device of claim 1 , wherein said diffractive features are separated by spaces and said spaces comprise exposed regions of said substrate material.
7. The optical device of claim 1 , wherein said diffractive features are separated by spaces and said spaces between said diffractive features are not covered by said layer of material.
8. The optical device of claim 1 , wherein said plurality of diffractive features comprise first, second, and third diffractive features laterally displaced with respect to each other, said second diffractive feature disposed between the first and the third diffractive features.
9. The optical device of claim 8 , wherein said layer of material has a different thickness over each of said first, second, and third diffractive features.
10. The optical device of claim 8 , wherein the thickness of said layer of material over said third diffractive feature is higher than the thickness of said layer of material over said second diffractive feature, and the thickness of said layer of material over said second diffractive feature is higher than the thickness of said layer of material over said first diffractive feature.
11. The optical device of claim 8 , wherein said layer of material has the same thickness over said first, second, and third diffractive features.
12. The optical device of claim 8 , wherein the height of said third diffractive feature is higher than the height of said second diffractive feature, and the height of said second diffractive feature is higher than the height of said first diffractive feature.
13. The optical device of claim 1 , wherein the thickness of said substrate is graded, or wherein the thickness of said layer of material is graded.
14. The optical device of claim 1 , wherein said waveguide is included in an eyepiece for a head mounted display, or wherein said waveguide is included in a stack of waveguides in said eyepiece.
15. The optical device of claim 1 , wherein the diffractive features are arranged in a 1D array.
16. The optical device of claim 1 , wherein the diffractive features are arranged in a 2D array.
17. The optical device of claim 1 , wherein said plurality of diffractive features are included in an in-coupling optical element disposed so as to receive light from an image source and couple said light into said substrate to be guided therein.
18. The optical device of claim 1 , wherein said plurality of diffractive features are included in a light distributing optical element disposed so as to receive light from an image source that is guided in said substrate and direct said light to an out-coupling optical element to be coupled out of said substrate.
19. The optical device of claim 1 , wherein said plurality of diffractive features are included in an out-coupling optical element disposed so as to receive light from an image source that is guided in said substrate and couple said light out of said substrate.