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. A waveguide may be transparent and may comprise a substrate comprising a first material having a first refractive index greater than about 2.0. Diffractive features may be formed, on the substrate, of a second material having a second refractive index that is lower than the first refractive index. A third material may be disposed over the diffractive features and may have a third refractive index that is higher than the second refractive index.
1 . An optical device comprising:
a substrate comprising a first material having a first refractive index greater than about 2.0, wherein the substrate comprises a waveguide that is transparent to visible light;
a plurality of diffractive features formed on a surface of the substrate, the diffractive features formed of a second material having a second refractive index lower than the first refractive index, wherein the surface of the substrate slopes downwards from one end of the plurality of diffractive features to an other end of the plurality of diffractive features, wherein a thickness of the substrate decreases as the surface slopes downwards; and
a third material disposed over the plurality of diffractive features, the third material having a third refractive index higher than the second refractive index.
2 . The optical device of claim 1 , wherein the first material comprises at least one of lithium niobate or silicon carbide.
3 . The optical device of claim 1 , wherein the first refractive index is at least about 2.3.
4 . The optical device of claim 1 , wherein the second material comprises photoresist.
5 . The optical device of claim 1 , wherein the second refractive index is less than about 1.8.
6 . The optical device of claim 5 , wherein the second refractive index is between about 1.2 and about 1.8.
7 . The optical device of claim 6 , wherein the second refractive index is about 1.5.
8 . The optical device of claim 1 , wherein the third refractive index is at least about 2.3.
9 . The optical device of claim 1 , wherein the third material comprises at least one of lithium niobate or silicon carbide.
10 . The optical device of claim 1 , wherein the plurality of diffractive features comprises a blazed diffractive grating.
11 . The optical device of claim 1 , wherein the plurality of diffractive features are asymmetrically shaped.
12 . The optical device of claim 1 , wherein more of the third material is on a first side of at least one of the diffractive features than on a second side of the at least one of the diffractive features.
13 . The optical device of claim 1 , wherein the plurality of diffractive features are arranged in a one-dimensional array.
14 . The optical device of claim 1 , wherein the plurality of diffractive features are arranged in a two-dimensional array.
15 . The optical device of claim 1 , wherein the plurality of diffractive features are included in an in-coupling optical element arranged to receive light and couple the light into the waveguide to be guided therein.
16 . The optical device of claim 1 , wherein the plurality of diffractive features are included in an out-coupling optical element arranged to couple, out of the waveguide, at least a portion of light being guided within the waveguide.
17 . The optical device of claim 1 , wherein a height of individual ones of the diffractive features increases as a thickness of the substrate decreases.