Ultra-large bandwidth fully polarized photodetectors based on displacement-induced chiral dielectric metasurfaces.

The polarization of light is enriched with a large amount of important structural information of materials, but it cannot be directly accessed by photodetectors. Although fully polarized photodetectors based on chiral metasurface filters can solve the challenge of polarized light signal acquisition, the effective bandwidth in the near-infrared band generally does not exceed 80 nm, which severely limits the overall signal capacity of the devices. We have investigated the equivalent electric field direction distribution pattern of the metasurface by varying the distance between two short arms in the unit cell of the metasurface, realizing a great leap in the spectrum from zero chirality to very large chirality with a bandwidth of 200 nm. In addition, combining this chiral metasurface with an InGaAs/InP intensity photodetector enables average errors of the degree of circular polarization of -18. The large bandwidth fully polarized photodetectors are expected to lead the way in the field of polarization modulation on nanophotonic platforms.