Self-aligned nano-pillar coatings and method of manufacturing
Meta-surface devices may be advantageously used for miniaturization, planar and thin film, high spatial resolution, and dense integration into optical devices. They have the potential to be used for steering a beam propagation direction, shaping wave-front light, and imparting information for application such as sensing, imaging, light detection, and ranging. However, meta-surface devices may have poor overall efficiency when compared with traditional optical devices. Embodiments of this disclosure relate to meta-surface devices including a pattern of high-index pillars with a low-index coating. Advantageously, the low-index coating may improve optical efficiency of the meta-surface devices which may make these meta-surface devices suitable for a variety of applications.
1 . A meta-surface device comprising:
a substrate;
a pattern of high-index pillars formed on the substrate; and
a coating of low-index material overlapping with the high-index pillars, wherein the coating of low-index material has a lower refractive index than the high-index pillars; wherein the coating of low-index material is in direct contact with the high-index pillars wherein the coating of low-index material is coated only on top surfaces of the high-index pillars;
a low-index encapsulation material, wherein the coating of low-index material is positioned between the low-index encapsulation material and the high-index pillars; and
a second low-index coating located between the high-index pillars and the substrate.
2 . The meta-surface device of claim 1 ,
wherein the pattern of high-index pillars comprises silicon, germanium, gallium phosphorus, gallium arsenic, gallium antimony, indium phosphorus, indium arsenic, indium antimony, titanium oxide, silicon nitride, or germanium-antimony-tellurium; and
wherein the coating of low-index material comprises aluminum oxide, silicon oxide, magnesium oxide, magnesium fluoride, silicon nitride, or hafnium oxide.
3 . The meta-surface device of claim 1 , wherein the high-index pillars are surrounded by the low-index encapsulation material.
4 . The meta-surface device of claim 1 , wherein the coating of low-index material comprises a multi-layer low-index material.
5 . The meta-surface device of claim 4 , wherein the multi-layer low-index material comprises two or more layers of low-index material each having a refractive index lower than the high-index pillars.
6 . The meta-surface device of claim 1 , wherein the substrate comprises lower refractive index than the refractive index of the high-index pillars.
7 . The meta-surface device of claim 1 , wherein the coating of low-index material is located on a side of the high-index pillars opposite to the substrate.
8 . The meta-surface device of claim 1 , wherein the coating of low-index material is located between the high-index pillars and the substrate.
9 . The meta-surface device of claim 1 , wherein the coating of low-index material is located both on a side of the high-index pillars opposite to the substrate and between the high-index pillars and the substrate.
10 . The meta-surface device of claim 1 , wherein the coating of low-index material is conformally coated on the top and side surfaces of the high-index pillars.
11 . The meta-surface device of claim 1 , wherein the coating of low-index material is coated only on top surfaces of the high-index pillars.
12 . The meta-surface device of claim 1 , wherein the high-index pillars each reside within a plurality of openings in the substrate.
13 . The meta-surface device of claim 12 , wherein the coating of low-index material is conformally coated on the substrate including the plurality of openings.
14 . The meta-surface device of claim 13 , wherein portions of the coating of low-index material are between the substrate and the high-index pillars.
15 . The meta-surface device of claim 1 , wherein the coating of low-index material comprises one or more transverse dimensions about equal to one or more transverse dimensions of the high-index pillars.
16 . The meta-surface device of claim 1 , wherein the high-index pillars comprise a semiconductor or chalcogenide material and the coating of low-index material comprises a lower index dielectric or oxide.
17 . The meta-surface device of claim 1 , wherein the coating of low-index material has a refractive index between 1.46 and 2.1.
18 . The meta-surface device of claim 17 , wherein the high-index pillars have a refractive index above 1.8.
19 . The meta-surface device of claim 18 , wherein the high-index pillars have a refractive index above 2.5.
20 . The meta-surface device of claim 1 , wherein the second low-index coating is a continuous layer coating the substrate directly contacting the high-index pillars and the low-index encapsulation material.