Geometric filterless photodetectors for mid-infrared spin light

Free-space circularly polarized light (CPL) detection, requiring polarizers and waveplates, has been well established, while such spatial degree of freedom is unfortunately absent in integrated on-chip optoelectronics. So far, those reported filterless CPL photodetectors suffer from the intrinsic small discrimination ratio, vulnerability to non-CPL field components, low responsivity. Here, we report a distinct paradigm geometric mid-infrared exhibiting colossal close-to-perfect CPL-specific response, zero-bias responsivity 392 V/W at room temperature, detectivity ellipticity down 0.03$^o$ Hz$^{-1/2}$. Our approach employs plasmonic nanostructures array with judiciously designed symmetry, assisted by graphene ribbons electrically read their near-field optical information. This geometry-empowered recipe for infrared provides robust, direct, strict, high-quality solution detection unlocks new opportunities functional optoelectronic devices.