METASURFACES FOR REDIRECTING LIGHT AND METHODS FOR FABRICATING

• US 20170131460A1
• Filed: 11/02/2016
• Published: 05/11/2017
• Est. Priority Date: 11/06/2015
• Status: Active Grant

• Current Assignee: Magic Leap, Inc.
• Original Assignee: Magic Leap, Inc.
• Inventors: Lin, Dianmin, St. Hilaire, Pierre, Peroz, Christophe, Poliakov, Evgeni, Melli, Mauro
• Granted Patent: US 11,231,544 B2
• Time in Patent Office: Days
• CPC Class Codes: G02B 2027/0134 of stereoscopic type
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 5/1823 in an overlapping or superposed manner
• CPC Class Codes: G02B 6/00 Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
• CPC Class Codes: G02B 6/0013 Means for improving the coupling-in of light from the light source into the light guide coupling light into light guides in general G02B6/42
• CPC Class Codes: G02B 6/0026 Wavelength selective element, sheet or layer, e.g. filter or grating
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area
• CPC Class Codes: G02B 6/1226 involving surface plasmon interaction
• CPC Class Codes: G02B 6/29316 Light guides comprising a diffractive element, e.g. grating in or on the light guide such that diffracted light is confined in the light guide G02B6/02057, G02B6/29332, G02B6/29356 take precedence

Abstract

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.

Claims

1. A method for forming an optical waveguide, the method comprising:

forming a metasurface, wherein forming the metasurface comprises;

providing an optically transmissive resist layer overlying an optically transmissive substrate;

patterning the resist with a pattern comprising protrusions and intervening gaps, wherein the protrusions have a pitch in a range of 10 nm to 600 nm; and

depositing an optically transmissive material on the protrusions and into the gaps between the protrusions.

2. The method of claim 1, wherein the optically transmissive material is amorphous.

3. The method of claim 1, wherein depositing the optically transmissive material forms spaced apart plateaus of the optically transmissive material above the protrusions.

4. The method of claim 1, wherein the optically transmissive material has a higher refractive index than either the patterned resist or the substrate.

5. The method of claim 4, wherein the refractive index of the optically transmissive material is higher than 1.7.

6. The method of claim 4, wherein the optically transmissive material is a resist.

7. The method of claim 1, wherein the optically transmissive substrate is a waveguide.

8. The method of claim 1, wherein patterning the resist comprises imprinting the pattern into the resist.

9. The method of claim 1, wherein depositing the optically transmissive material comprises spin coating the optically transmissive material on the patterned resist.

10. The method of claim 1, wherein depositing the optically transmissive material comprises performing a conformal deposition or a directional deposition of the optically transmissive material.

11. The method of claim 10, wherein the conformal deposition comprises chemical vapor deposition or atomic layer deposition of the optically transmissive material.

12. The method of claim 10, wherein the directional deposition comprises evaporation or sputtering the optically transmissive material.

13. The method of claim 1, wherein the total width is in a range of 300 to 500 nm.

14. The method of claim 1, wherein depositing an optically transmissive material deposits the optically transmissive material to a thickness of 10 nm-1 μ

m above the protrusions.

15. The method of claim 1, wherein the protrusions comprise steps on two levels.

16. A display system comprising:

a waveguide;

a light incoupling optical element disposed on a surface of the waveguide, the light incoupling optical element comprising;

a multilevel metasurface comprising;

a plurality of spaced apart protrusions having a pitch and formed of a first optically transmissive material;

a second optically transmissive material over and between the spaced apart protrusions.

17. The display system of claim 16, wherein the pitch of the protrusions varies across the surface of the waveguide.

18. The display system of claim 16, further comprising an image injection device configured to inject light comprising image information into the waveguide.

19. The display system of claim 16, wherein the waveguide is one of a stack of waveguides, wherein each of the stack of waveguides comprises an associated multilevel metasurface.

20. The display system of claim 19, 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.

21. The display system of claim 16, wherein the first optically transmissive material comprises a resist.

22. The display system of claim 16, wherein each protrusion and space between an immediately neighboring protrusions define a total width of 10-600 nm.

23. The display system of claim 16, wherein the second optically transmissive material forms the spaced apart plateaus over the protrusions.

24. The display system of claim 16, wherein the first and second optically transmissive materials are amorphous.

25. The display system of claim 16, wherein the second optically transmissive material has a higher refractive index than either the first optically transmissive material or material forming the waveguide.

26. The display system of claim 25, wherein the second optically transmissive material has a refractive index greater than 1.7.

27. The display system of claim 25, wherein the optically transmissive material comprises a semiconductor.

28. The display system of claim 27, wherein the optically transmissive material comprises silicon.

29. The display system of claim 28, wherein the optically transmissive material comprises silicon nitride or silicon carbide.

30. The display system of claim 25, wherein the optically transmissive material comprises an oxide.

31. The display system of claim 25, wherein the optically transmissive material comprises a metal oxide.

32. The display system of claim 31, wherein the optically transmissive material comprises titanium oxide, zirconium oxide, or zinc oxide.

33. The display system of claim 16, wherein the metasurface is a bi-level metasurface.

34. The display system of claim 16, wherein the metasurface is a tri-level or higher level metasurface.

35. A display system comprising:

a waveguide;

a light outcoupling optical element disposed on a surface of the waveguide, light outcoupling optical element comprising;

a multilevel metasurface comprising;

a plurality of spaced apart protrusions having a pitch and formed of a first optically transmissive material;

a second optically transmissive material over and between the spaced apart protrusions.

36. The display system of claim 35, wherein the pitch of the protrusions varies across the surface of the waveguide.

37. The display system of claim 35, further comprising an image injection device configured to inject light comprising image information into the waveguide.

38. The display system of claim 35, wherein the waveguide is one of a stack of waveguides, wherein each of the stack of waveguides comprises an associated multilevel metasurface.

39. The display system of claim 38, 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

40. The display system of claim 35, further comprising a light incoupling optical element disposed on a surface of the waveguide, wherein both of the light incoupling and light outcoupling optical elements comprise a multilevel metasurface.

41. The display system of claim 35, wherein each protrusion and a space between an immediately neighboring protrusions define a total width of 200-500 nm.

42. The display system of claim 35, wherein the second optically transmissive material forms the spaced apart plateaus over the protrusions.

43. The display system of claim 35, wherein the first and second optically transmissive materials are amorphous.

44. The display system of claim 35, wherein the first optically transmissive material is a nanoimprint resist.

45. The display system of claim 35, wherein the second optically transmissive material has a higher refractive index than either the first optically transmissive material or material forming the waveguide.

46. The display system of claim 45, wherein the second optically transmissive material has a refractive index greater than 1.7.

47. The display system of claim 46, wherein the optically transmissive material comprises a semiconductor.

48. The display system of claim 47, wherein the optically transmissive material comprises silicon.

49. The display system of claim 48, wherein the optically transmissive material comprises silicon nitride or silicon carbide.

50. The display system of claim 46, wherein the optically transmissive material comprises an oxide.

51. The display system of claim 50, wherein the optically transmissive material comprises a metal oxide.

52. The display system of claim 51, wherein the optically transmissive material comprises titanium oxide, zirconium oxide, or zinc oxide.

53. The display system of claim 35, wherein the waveguide is formed of a material having a refractive index of 1.6 or higher.

54. The display system of claim 35, wherein the protrusions are single level structures.

55. The display system of claim 35, wherein the protrusions are stepped, multi-level structures.