Wavelength-scalable mid-infrared photodetectors based on photon-assisted tunneling in MIM metasurfaces

We propose zero-bias, wavelength-scalable, and polarization-selective mid-infrared photodetectors based on metal–insulator–metal (MIM) metasurfaces. Specifically, these photodetectors leverage the second-order quantum conductivity sourced from photon-assisted tunneling and strong electric field localization in the MIM nanojunction to achieve efficient optical rectification. We show that by tailoring metasurface geometry, the incident infrared radiation can be efficiently coupled into the MIM heterojunction, with certain wavelength and polarization selectivity, and the optical rectification effect can be achieved with a photoresponsivity as high as tens of mA/W. Such results may pave a promising route toward the next-generation mid-infrared photodetection and energy harvesting.