Metalens with corrected phase
View Patent ↗A computer-implemented method is provided for designing a metalens. The metalens has a metasurface including nano-structures arranged on a substrate based on preliminary simulation data. The method includes partitioning the nano-structures into overlapping d-unit supercells such that every non-perimeter nano-structure is at the center of one d-unit supercell, computing a differentiable mapping function of the d-unit supercells that predicts the near-field over the unit cell at the center of the supercell from the design parameters of all the nanostructures in the supercell, jointly tuning the design parameters of all unit cells in the metalens to better approximate a target near field distribution over the entire metalens, by using a Jacobian of partial derivatives provided by the mapping function to solve for a locally optimal correction of all design parameters, and generating a fabricable design of the metalens based on the optimized parameters.
1 . A computer-implemented method for designing a metalens having a metasurface including nano-structures arranged on a substrate based on preliminary simulation data, wherein the method uses a processor coupled with a memory storing a target near field profile, the preliminary simulation data of the metalens and instructions implementing the method, wherein the preliminary simulation data represent design parameters including geometry and orientation angle with respect to the nano-structures on the metalens, wherein the instructions, when executed by the processor, carry out at steps of the method, comprising:
partitioning the nano-structures into overlapping d-unit supercells such that every non-perimeter nano-structure is at a center of one d-unit supercell;
computing a differentiable mapping function of the d-unit supercells that predicts the near-field over the unit cell at the center of the supercell from the design parameters of all the nanostructures in the supercell, by fitting an interpolator to preliminary simulation data of the d-unit supercells;
jointly tuning the design parameters of all unit cells in the metalens to better approximate a target near field distribution over the entire metalens, by using a Jacobian of partial derivatives provided by the mapping function to solve for a locally optimal correction of all design parameters; and
generating a fabricable design of the metalens based on the optimized parameters.
2 . The method of claim 1 , wherein the metasurface is arranged into grids of unit cells that partition a plane into rectangular, hexagonal, triangular or phyllotactic shapes.
3 . The method of claim 2 , wherein the phyllotactic is formed by a double-spiral pattern.
4 . The method of claim 1 , wherein the substrate is made from silicon dioxide.
5 . The method of claim 1 , wherein the nano-structures are made from titanium dioxide.
6 . The method of claim 1 , wherein the computing step continues until a scale of the design parameter corrections falls below fabrication tolerances.
7 . The method of claim 1 , wherein in the computing step, an interpolator function is used to predict a near field phase distribution over each of the unit cells.
8 . The method of claim 7 , wherein the computing step continues until the near field phase distribution matches the target near field phase distribution within a target error tolerance.
9 . The method of claim 1 , wherein interpolations are performed for one-dimensional subsets of the d-unit supercells to obtain interpolation functions and the obtained interpolation functions are averaged to provide predictions and gradients for two-dimensional d-unit supercells.
10 . The method of claim 1 , wherein the d-unit supercells are different combinations of orientations of the set of nano-fins, wherein the interaction of each of the d-unit supercells with an incident wavefront is simulated by solving Maxwell's equations.