Metasurfaces for redirecting light and methods for fabricating
A display system comprises a waveguide having light incoupling or light outcoupling optical elements formed of a metasurface. The metasurface is a multilevel (e.g., bi-level) structure having a first level defined by spaced apart protrusions formed of a first optically transmissive material and a second optically transmissive material between the protrusions. The metasurface also includes a second level formed by the second optically transmissive material. The protrusions on the first level may be patterned by nanoimprinting the first optically transmissive material, and the second optically transmissive material may be deposited over and between the patterned protrusions. The widths of the protrusions and the spacing between the protrusions may be selected to diffract light, and a pitch of the protrusions may be 10-600 nm.
1. A near-eye display system comprising:
a waveguide configured to propagate and output light that conveys image information;
an optical element disposed on a surface of the waveguide, the optical element configured to redirect the light, wherein the redirecting includes at least one of in-coupling the light into the waveguide or out-coupling the light from the waveguide, the optical element comprising:
a multilevel metasurface comprising:
a plurality of spaced-apart protrusions protruding outward from the surface of the waveguide, the plurality of spaced-apart protrusions having a pitch and formed of a first optically transmissive material; and
an optically transmissive resist between the spaced-apart protrusions, wherein the optically transmissive resist at least partly fills the spaces between the protrusions without extending over the protrusions.
2. The near-eye display system of claim 1 , wherein the plurality of spaced-apart protrusions are formed of resist having a different refractive index than the optically transmissive resist between the spaced-apart protrusions.
3. The near-eye display system of claim 2 , wherein the optically transmissive resist between the spaced-apart protrusions has a higher refractive index than material forming the plurality of spaced-apart protrusions.
4. The near-eye display system of claim 3 , wherein the optically transmissive resist between the spaced-apart protrusions has a higher refractive index than material forming the waveguide.
5. The near-eye display system of claim 1 , wherein upper surfaces of the plurality of spaced-apart protrusions and the optically transmissive resist between the spaced-apart protrusions define a planar surface.
6. The near-eye display system of claim 1 , wherein the optically transmissive resist between the spaced-apart protrusions extends over the plurality of spaced-apart protrusions to define a continuous layer of resist above the plurality of spaced-apart protrusions.
7. The near-eye display system of claim 1 , further comprising a layer of resist underlying the plurality of spaced-apart protrusions.
8. The near-eye display system of claim 1 , wherein the pitch of the protrusions varies across the surface of the waveguide.
9. The near-eye display system of claim 1 , further comprising an image injection device configured to inject light comprising the image information into the waveguide.
10. The near-eye display system of claim 9 , wherein the optical element is an in-coupling optical element, wherein the image injection device is configured to inject light into the waveguide through the in-coupling optical element.
11. The near-eye display system of claim 1 , wherein the waveguide is one of a stack of waveguides, wherein each of the stack of waveguides comprises an associated multilevel metasurface.
12. The near-eye display system of claim 11 , wherein the associated multilevel metasurfaces of at least some of the waveguides are configured to redirect light of different ranges of wavelengths than the associated multilevel metasurfaces of others of the waveguides.
13. The near-eye display system of claim 1 , wherein the pitch is in a range of 10-600 nm.
14. The near-eye display system of claim 1 , wherein the metasurface is a bi-level metasurface.
15. The near-eye display system of claim 1 , wherein the metasurface is a tri-level metasurface.
16. The near-eye display system of claim 1 , wherein the pitch is less than a wavelength of the light being redirected.