Metasurface, metalens, and metalens array with controllable angular field-of-view
View Patent ↗A metalens and a metalens array having a bounded angular field of view are disclosed. The metalens includes a substrate and a two-dimensional (2D) grid over the substrate to divide the substrate into a 2D array of meta-units. Each meta-unit in the 2D array includes a nanostructure and a portion of the substrate that supports the nanostructure. Moreover, each meta-unit is configured with an angular-dependent transmission or reflection coefficient that decreases with an increasing incident angle of an illumination. Moreover, the metalens passes an incident light having an incident angle less than a cutoff angle and rejects an incident light having an incident angle greater than the cutoff angle. The metalens can be used a base unit for constructing a metalens array by tiling copies of the metalens into a 2D array of the metalens to achieve a significantly larger field-of-view.
1 . A metalens having a bounded angular field of view, comprising:
a substrate; and
a two-dimensional (2D) grid, over the substrate, dividing the substrate into a 2D array of meta-units, wherein each meta-unit in the 2D array comprises:
a nanostructure; and
a portion of the substrate that supports the nanostructure,
wherein each meta-unit is configured with an angular-dependent transmission or reflection coefficient that decreases with an increasing incident angle of an illumination and a predetermined cutoff angle when the angular-dependent transmission or reflection coefficient becomes substantially zero; and
wherein the metalens passes an incident light having an incident angle less than the predetermined cutoff angle and rejects an incident light having an incident angle greater than the predetermined cutoff angle.
2 . The metalens of claim 1 , wherein the nanostructure includes one of:
a nanapost; and
a nanohole/nanowell.
3 . The metalens of claim 2 , wherein the nanostructure is a nanopost having a circular cross-section and specified by a diameter and a height.
4 . The metalens of claim 3 , wherein different nanoposts inside different meta-units in the 2D array have different diameters.
5 . The metalens of claim 1 , wherein the metalens has a center location, and wherein a plurality of nanoposts in the 2D array that have substantially the same distance to the center location have the same diameter.
6 . The metalens of claim 1 , wherein when the metalens is used for imaging an object, either the nanostructure side of the metalens or the substrate side of the metalens can be selected to face the object.
7 . The metalens of claim 1 , wherein each nanostructure can be positioned inside the respective meta-unit either at the center of the meta-unit or at an off-centered position.
8 . The metalens of claim 1 , wherein the metalens is configured to have a spatial phase-shift profile for a given wavelength that mimics a target spatial phase-shift profile of a conventional optical lens.
9 . The metalens of claim 8 , wherein each nanostructure inside a given meta-unit in the 2D array is configured to effectuate an amount of phase-shift on an incident light at the given wavelength based on the target spatial phase-shift profile and a distance between the nanostructure and the center location of the metalens.
10 . The metalens of claim 1 , wherein the nanostructure is made of polysilicon and wherein the substrate is made of fused silica.
11 . The metalens of claim 1 , wherein the metalens is used to construct a lens element within a compact optical imaging system configured for either transmission-mode or reflection-mode 2D imaging.
12 . The metalens of claim 1 , wherein the metalens is used to construct a lens element within a compact optical imaging system configured for transmission-mode or reflection-mode three-dimensional (3D) imaging.
13 . The metalens of claim 1 , wherein the 2D array of meta-units has a constant spacing between adjacent meta-units in one or both dimensions of the 2D array.
14 . A metasurface angular filter, comprising:
a substrate; and
a two-dimensional (2D) grid, over the substrate, dividing the substrate into a 2D array of meta-units, wherein each meta-unit in the 2D array comprises:
a nanostructure; and
a portion of the substrate that supports the nanostructure,
wherein each meta-unit in the 2D array of meta-units is configured with an angular-dependent transmission profile so that the metasurface angular filter:
passes incoming light wave having an angle of incident less than a predetermined acceptance angle; and
rejects or significantly attenuates incoming light wave having an angle of incident greater than the predetermined acceptance angle.
15 . The metasurface angular filter of claim 14 , wherein after passing through the metasurface angular filter, the angle of propagation of the first incoming light wave having an angle of incident less than a predetermined acceptance angle is substantially the same as the angle of incident.
16 . The metasurface angular filter of claim 14 , wherein the angular-dependent transmission profile is symmetric in the 2D plane of the 2D array of meta-units.