Metasurface-assisted 3D beam shaping for desired phase, amplitude, and polarization
Cascaded metasurfaces can control the phase, amplitude and polarization of an electromagnetic beam, shaping it in three dimensional configuration not achievable with other methods. Each cascaded metasurface has dielectric or metallic scatterers arranged in a period array. The shape of the scatterers determines the three dimensional configuration of the output beam and is determined with iterative calculations through computational simulations.
1. A method comprising:
a) selecting a desired three dimensional (3D) shape of an electromagnetic beam, comprising a desired phase, a desired amplitude, and a desired polarization;
b) selecting a parametric shape for an array of scatterers for each metasurface of one or more metasurfaces;
c) calculating, by a computer, a simulated 3D shape of a simulated electromagnetic beam scattered by the one or more metasurfaces;
d) calculating a difference between the desired 3D shape and the simulated 3D shape;
e) iterating steps b)-d) until a threshold minimum value for the difference is achieved; and
f) fabricating the one or more metasurfaces based on the parametric shape, once the threshold minimum value for the difference is achieved;
wherein the desired 3D shape is a periodic 3D shape, and step a) comprises:
a1) defining the desired amplitude within a unit cell of the periodic 3D shape; and
a2) periodically copying the periodic 3D shape to form a Bravais lattice structure.
2. The method of claim 1 , wherein:
selecting the parametric shape comprises selecting a height, a first lateral dimension, and a second lateral dimension, the second lateral dimension being shorter than the first lateral dimension.
3. The method of claim 1 , wherein the one or more metasurfaces comprise a plurality of metasurfaces, and step b) comprises:
g) selecting a different parametric shape for each metasurface of the plurality of metasurfaces; and
h) cascading each metasurface of the plurality of metasurfaces to form a metasurface device.
4. The method of claim 1 , wherein steps a1)-a2) comprise:
defining a normalized intensity above a threshold value over a volume with a finite cross-section around vertices and sides of the Bravais lattice structure.
5. The method of claim 4 , wherein the threshold value of the normalized intensity is greater than 0.5.
6. A method comprising:
a) selecting a desired three dimensional (3D) shape of an electromagnetic beam, comprising a desired phase, a desired amplitude, and a desired polarization;
b) selecting a parametric shape for an array of scatterers for each metasurface of a plurality of metasurfaces;
c) calculating, by a computer, a simulated 3D shape of a simulated electromagnetic beam scattered by the plurality of metasurfaces;
d) calculating a difference between the desired 3D shape and the simulated 3D shape;
e) iterating steps b)-d) until a threshold minimum value for the difference is achieved; and
f) fabricating the plurality of metasurfaces based on the parametric shape, once the threshold minimum value for the difference is achieved;
wherein the plurality of metasurfaces comprises a first metasurface comprising dielectric scatterers, and a second metasurface comprising metallic scatterers.
7. The method of claim 6 , wherein the array of dielectric scatterers and the array of metallic scatterers have a matching periodic lattice.
8. The method of claim 6 , wherein:
selecting the parametric shape comprises selecting a height, a first lateral dimension, and a second lateral dimension, the second lateral dimension being shorter than the first lateral dimension.
9. The method of claim 6 , wherein the one or more metasurfaces comprise a plurality of metasurfaces, and step b) comprises:
i) selecting a different parametric shape for each metasurface of the plurality of metasurfaces; and
j) cascading each metasurface of the plurality of metasurfaces to form a metasurface device.