Resonant-grating reflection extended to wide-band, large-aperture beams by waveguide-mode coalescence

Abstract

The resonant reflection of a free-space beam from a slab waveguide grating is rendered high bandwidth and angularly robust by using a bimodal high index waveguide. A deep double-sided corrugation gives rise to the coalescence of the resonant reflection peaks resulting in a top-hat reflection spectrum. A low-cost waveguide technology based on solar cell amorphous silicon is demonstrated in the near infrared in a polarizer application.

Recent Advances in Resonant Waveguide Gratings

“…These authors investigated as well the performances of RWG polarizers made with different low‐losses materials, such as silicon, silicon nitride, and titanium dioxide . If the RWG is built from a very high‐index bimodal waveguide having a deep double‐sided corrugation, a coalescence of the reflection peaks of TE0 and TE1 modes suppresses the dip between them, leading to a wideband and wide angular polarizer that works with low temporal and spatial coherence light sources such as LEDs . Ultra‐sparse RWGs (illustrated in Figure a,b) made with a very low duty cycle (10%) can be used as well as effective wideband polarizers and be designed for different spectral domains …”

“…[299] If the RWG is built from a very high-index bimodal waveguide having a deep double-sided corrugation, a coalescence of the reflection peaks of TE0 and TE1 modes suppresses the dip between them, leading to a wideband and wide angular polarizer that works with low temporal and spatial coherence light sources such as LEDs. [300] Ultra-sparse RWGs (illustrated in Figure 15a,b) made with a very low duty cycle (10%) can be used as well as effective wideband polarizers and be designed for different spectral domains. [301] Fully deterministic depolarizers can also be implemented using thin RWGs for quasi-monochromatic light, by Figure 15.…”

Realization of a PT-symmetric microchip laser in the polarization space using nanostructured laser mirrors

“…The interesting part of our design is what happens at the boundary between these two areas, where a pair of eigenvectors and eigenvalues coalesce into one state, a so-called exceptional point. To obtain PT symmetry in polarization space in our Fabry Perot resonator, we use resonant grating mirrors [31] to introduce diattenuation and birefringence at normal incidence angles in the resonator without inserting intracavity elements. With the control over the angle between the two mirrors' principal axes (𝛼), we can go between broken and unbroken symmetry and locate the exceptional point at the boundary.…”