Design of computer-generated holograms based on semi-rigorous simulations of sub-wavelength structures.

Conventional design methods for computer-generated holograms often rely on the scalar diffraction theory because the calculation effort of rigorous simulations is too high. But for sub-wavelength lateral feature sizes or large deflection angles, the performance of realized elements will show distinct deviations from the expected scalar behavior. We propose a new design method that overcomes this issue by incorporating high-speed semi-rigorous simulation techniques that allow the modeling of light propagation at an accuracy close to the rigorous methods. This includes an approach to solve the inverse problem of calculating a geometric structure that is able to form a certain physical field distribution.

Ultrafast farfield simulation of non-paraxial computer generated holograms.

The simulation of large-area diffractive optical elements (DOEs) is challenging when non-paraxial propagation and coupling effects between neighboring structures shall be considered. We developed a novel method for the farfield simulation of DOEs, especially computer-generated holograms (CGHs) with lateral feature sizes in the wavelength range. It uses a machine learning approach to predict the optical function based on geometry parameters. Therefore, training data are calculated by physical simulation methods to create a linear regression model. With the trained model a very fast computation of the farfield is possible with high conformity to results of rigorous methods.

Macroscopic wave-optical simulation of dielectric metasurfaces.

We propose a novel method for the wave-optical simulation of diffractive optical elements (DOEs) like metasurfaces or computer-generated holograms (CGHs). Existing techniques mostly rely on the assumption of local periodicity to predict the performance of elements. The utilization of a specially adapted finite-difference beam propagation method (BPM) allows the semi-rigorous simulation of entire DOEs within a reasonable runtime due to linear scaling with the number of grid points. Its applicability is demonstrated by the simulation of a metalens and a polarization-dependent beamsplitter, both based on effective-medium metasurfaces. A comparison shows high conformity to rigorous simulations.