Light refocusing with up-scalable resonant waveguide gratings in confocal prolate spheroid arrangements

TLDR: In this article, the authors proposed a design method to create large patterns of waveguide gratings able to filter, steer, and focus the light from one point source to another, where the two focal points are the source point and the observation point, respectively.

Abstract: Resonant waveguide gratings (RWGs) are thin-film structures, where coupled modes interfere with the diffracted incoming wave and produce strong angular and spectral filtering The combination of two finite-length and impedance matched RWGs allows the creation of a passive beam steering element, which is compatible with up-scalable fabrication processes Here, we propose a design method to create large patterns of such elements able to filter, steer, and focus the light from one point source to another The method is based on ellipsoidal mirrors to choose a system of confocal prolate spheroids where the two focal points are the source point and observation point, respectively It allows finding the proper orientation and position of each RWG element of the pattern, such that the phase is constructively preserved at the observation point The design techniques presented here could be implemented in a variety of systems, where large-scale patterns are needed, such as optical security, multifocal or monochromatic lenses, biosensors, and see-through optical combiners for near-eye displays