Highly efficient optics/microwave beam splitter based on frequency selective surface

The development of hybrid optics/microwave communication systems puts forward a new requirement for beam splitters to efficiently transmit microwave signals and simultaneously reflect optical signals. Owing to mechanical constraints, the physical thickness of beam splitters is of the order of tens of millimeters. The corresponding electrical thickness has the same order of magnitude as microwave wavelengths, and the resulting multi-beam interference effect significantly reduces the microwave transmittance, impacting the beam splitting quality.This study presents a new optics/microwave beam splitter based on the ability of the frequency selective surface(FSS) to shape the resonant curve. A beam splitter sample,whose physical thickness and substrate material are 20 mm and quartz glass, respectively, is designed, simulated, fabricated, and characterized to validate the feasibility of this strategy. The measured results show that the minimum microwave transmittance between 35 and 36.5 GHz with an incidence angle of 45° under TE polarization is 86.43%, and the mean value of the reflectance spectra from 450 to 900 nm and that from 7.7 to 10.5 μm both exceed 96%. This FSS-based optics/microwave beam splitter is expected to play a key role in hybrid optics/microwave communication systems.