Optical elements that include a metasurface
An apparatus includes an optical element that has an optical metasurface including meta-atoms. In some instances, at least some of the meta-atoms have a first height and others of the meta-atoms have a second height that differs from the first height. In some instances, each meta-atom has a cross-section composed of a first metamaterial surrounded laterally by a second different metamaterial. Techniques for manufacturing such optical elements also are disclosed.
1 . An apparatus comprising:
a substrate;
an optical element comprising:
an optical metasurface on the substrate, the optical metasurface including meta-atoms,
wherein at least some of the meta-atoms have a first height and others of the meta-atoms have a second height that differs from the first height, and
wherein a metamaterial of each of the meta-atoms has an annular shape in a top view; and
a polymeric layer between the substrate and the metamaterial of each of the meta-atoms, wherein sidewalls of the polymeric layer are aligned with sidewalls of the metamaterial, and wherein the polymeric layer exposes portions of the substrate spaced apart from the meta-atoms.
2 . The apparatus of claim 1 wherein some of the meta-atoms have a third height that differs from the first height and from the second height.
3 . The apparatus of claim 1 wherein the metamaterial laterally surrounds a hollow interior of each of the meta-atoms.
4 . The apparatus of claim 1 wherein the metamaterial of each of the meta-atoms comprises a first metamaterial surrounded laterally by a second different metamaterial, wherein each of the first metamaterial and the second different metamaterial has an annular cross-section.
5 . The apparatus of claim 1 wherein the metamaterial has a high index of refraction and a low optical loss.
6 . A method of manufacturing an optical element comprising:
imprinting a polymeric layer that is disposed on a substrate, wherein the imprinting results in formation of projections, extending away from the substrate, of material of the polymeric layer;
forming meta-atoms comprising a first metamaterial layer, wherein forming the meta-atoms includes depositing the first metamaterial layer over the projections;
removing a portion of the first metamaterial layer to expose a surface of the projections of the material of the polymeric layer; and
removing a residual portion of the polymeric layer, to form a second polymeric layer between the substrate and the first metamaterial layer of each of the meta-atoms, wherein sidewalls of the second polymeric layer are aligned with sidewalls of the first metamaterial layer, and wherein the second polymeric layer exposes portions of the substrate spaced apart from the meta-atoms.
7 . The method of claim 6 wherein some of the meta-atoms have a first meta-atom height and other ones of the meta-atoms have a second meta-atom height that differs from the first meta-atom height.
8 . The method of claim 6 , wherein each of the meta-atoms has an annular cross-section.
9 . The method of claim 6 including:
depositing a second metamaterial layer in areas where the residual portion of the polymeric layer was removed, such that each of the meta-atoms has a solid cross-section.
10 . The method of claim 9 wherein the second metamaterial layer is composed of a same material as a material of the first metamaterial layer.
11 . The method of claim 9 wherein the second metamaterial layer is composed of a material that is different from a material of the first metamaterial layer.
12 . The method of claim 11 wherein the solid cross-section of each of the meta-atoms includes an annular portion composed of the first metamaterial layer surrounded laterally by a core portion composed of the second metamaterial layer.
13 . The method of claim 6 wherein forming the meta-atoms further includes depositing a second metamaterial layer over the projections, wherein the second metamaterial layer is composed of a different material from the first metamaterial layer, and wherein each of the meta-atoms includes a first annular ring composed of the first metamaterial layer and a second annular ring composed of the second metamaterial layer.
14 . The method of claim 6 , comprising:
after removing the residual portion of the polymeric layer, depositing an active medium material inside an annular shape of the first metamaterial layer of each of the meta-atoms.
15 . The method of claim 14 , wherein the active medium material is different from a material of the first metamaterial layer.
16 . The method of claim 14 , comprising:
after depositing the active medium material, removing a portion of the active medium material that is outside the annular shape of the first metamaterial layer of each of the meta-atoms, to expose a surface of the substrate.
17 . The method of claim 6 , wherein removing the residual portion of the polymeric layer comprises completely removing the polymeric layer from inside an annular shape of the first metamaterial layer of each of the meta-atoms.