Flat-top Brewster filter based on guided mode resonance effect

We have analyzed and discussed a flat-top Brewster filter that works in full conical mounting. Results reveal that flat-top reflection band can be formed by merging double peaks that corresponded to guided modes with different polarization states. Merging is achieved by adjusting the incident angle in the design. When the proposed single-layer waveguide grating structure is irradiated with transverse magnetic (TM) polarized plane wave at the Brewster angle, the filter has a highly efficient flat-top reflection spectral response with central wavelength of 547 nm, bandwidth of 15.5 nm (R > 90%), and sideband reflectance of