On-chip phase modulating thin film optical elements
A thin-film optical device disclosed herein includes a metalens able to modulate the phase of incident light. The metalens includes a thin-film layer having a first index of refraction, an embedded layer within the thin-film layer, and the embedded layer having a second index of refraction greater than or equal to 1.5 and less than or equal to 3.0 times the first index of refraction. The embedded layer may fill a plurality of holes formed on the thin film layer, with the depth, width, and spacing of holes all contribute to modulating the phase of light traveling through the metalens.
1. A metalens, comprising:
a first thin-film layer comprising a first index of refraction; and
a first embedded layer within the first thin-film layer and comprising a second index of refraction, a ratio of the second index of refraction to the first index of refraction being greater than or equal to 1.5 and less than or equal to 3.0; and
wherein the first embedded layer fills a plurality of holes in the first thin-film layer, and wherein the plurality of holes have a lattice spacing of substantially half a predetermined target wavelength between each other.
2. The metalens of claim 1 , wherein the metalens further comprises a second thin-film layer having a third index of refraction and a second embedded layer having a fourth index of refraction, the second embedded layer being within the second thin-film layer, and
wherein a ratio of the fourth index of refraction to the second index of refraction is greater than or equal to 1.5 and less than or equal to 3.0.
3. The metalens of claim 2 , wherein the metalens further comprises a third thin-film layer having a fifth index of refraction and a third embedded layer having a sixth index of refraction, the third embedded layer being within the third thin-film layer, and
wherein a ratio of the sixth index of refraction to the fifth index of refraction is greater than or equal to 1.5 and less than or equal to 3.0.
4. The metalens of claim 2 , wherein the metalens further comprises a third thin-film layer having a fifth index of refraction and a liquid-crystal embedded layer within the third thin-film layer, and
wherein the liquid-crystal embedded layer comprises a first state and a second state, the first state comprising a sixth index of refraction and a ratio of the sixth index of refraction to the fifth index of refraction being greater than or equal 1.5 and less than or equal 3, and the second state comprising a seventh index of refraction and a ratio of the seventh index of refraction to the fifth index of refraction being less than or equal to 1.5.
5. The metalens of claim 4 , wherein the third thin-film layer is between the first thin-film layer and the second thin-film layer, and
wherein a light path between the first thin-film layer and the second thin-film layer changes based on the liquid-crystal embedded layer changing from the first state to the second state.
6. The metalens of claim 1 , wherein the metalens transmits a predetermined range of wavelengths of light that is incident upon the metalens.
7. The metalens of claim 1 , wherein the metalens transmits light with a critical ray angle relative to a normal of a surface of the first thin-film layer of between 0 degrees and 45 degrees inclusive.
8. The metalens of claim 1 , further comprising an imaging pixel, wherein the metalens is disposed between the imaging pixel and an imaging target.
9. The metalens of claim 8 , wherein the metalens comprises at least a first array of metalenses, and
further comprising an array of imaging pixels, each imaging pixel comprising a corresponding metalens disposed between the imaging pixel and the imaging target.
10. The metalens of claim 8 , wherein at least one metalens comprises a field of view that includes an active area and a circuit area for the imaging pixel, and wherein the at least one metalens focuses incident light onto the active area of the imaging pixel.
11. The metalens of claim 1 , wherein the first embedded layer fills a hole in the first thin-film layer, and wherein a ratio of a depth of the hole in the first thin-film layer to a width of the hole in the first thin-film layer is between 1:1 and 1:10 inclusive.
12. An optoelectrical device, comprising:
a unit pixel comprising a metalens and an image sensor, the metalens comprising a first thin-film layer with a first index of refraction and a first embedded layer within the first thin-film layer and comprising a second index of refraction, the first embedded layer filling a first plurality of holes in the first thin-film layer; and
wherein a ratio of a depth of the first plurality of holes in the first thin-film layer to a width of the first plurality of holes in the first thin-film layer is less than or equal to 1:20.
13. The optoelectrical device of claim 12 , wherein a ratio of the second index of refraction to the first index of refraction is greater than or equal to 1.5 and less than or equal to 3.
14. The optoelectrical device of claim 12 , wherein the ratio of the depth of the first plurality of holes in the first thin-film layer to the width of the first plurality of holes in the first thin-film layer is between 1:3 and 1:6.
15. The optoelectrical device of claim 12 , wherein the first plurality of holes have a lattice spacing of substantially half a predetermined target wavelength between each other.
16. The optoelectrical device of claim 12 , wherein the metalens transmits a predetermined range of wavelengths of light that is incident upon the metalens.
17. The optoelectrical device of claim 12 , wherein the metalens transmits light with a critical ray angle relative to a normal of a surface of the first thin-film layer of between 0 degrees and 45 degrees, inclusive.
18. The optoelectrical device of claim 12 , wherein the metalens further comprises a second thin-film film layer having a third index of refraction and a second embedded layer having a fourth index of refraction, the second embedded layer filling a second plurality of holes in the second thin-film layer;
a third thin-film layer having a fifth index of refraction and a liquid-crystal embedded layer within the third thin-film layer, the liquid-crystal embedded layer filling a third plurality of holes in the third thin-film film layer; and
wherein the first plurality of holes, the second plurality of holes, and the third plurality of holes each have a lattice spacing of substantially half a predetermined target wavelength.
19. The optoelectrical device of claim 18 , wherein the liquid-crystal embedded layer comprises a first state and a second state, the first state comprising a sixth index of refraction and a ratio of the sixth index of refraction to the fifth index of refraction being greater than or equal 1.5 and less than or equal 3, and the second state comprising a seventh index of refraction and a ratio of the seventh index of refraction to the fifth index of refraction being less than or equal to 1.5.