▎ 摘　　要

Spectral imagers, the classic example being the color camera, are ubiquitous in everyday life. However, most such imagers rely on filter arrays that absorb light outside each spectral channel, yielding similar to 1/N efficiency for an N-channel imager. This is especially undesirable in thermal infrared (IR) wavelengths, where sensor detectivities are low. We propose an efficient and compact thermal infrared spectral imager comprising a metasurface composed of sub-wavelength-spaced, differently-tuned slot antennas coupled to photosensitive elements. Here, we demonstrate this idea using graphene, which features a photoresponse up to thermal IR wavelengths. The combined antenna resonances yield broadband absorption in the graphene exceeding the 1/N efficiency limit. We establish a circuit model for the antennas' optical properties and demonstrate consistency with full-wave simulations. We also theoretically demonstrate similar to 58% free space-to-graphene photodetector coupling efficiency, averaged over the 1050cm(-1) to 1700cm(-1) wavenumber range, for a four-spectral-channel gold metasurface with a 0.883 mu m by 6.0 gm antenna pitch. This research paves the way towards compact CMOS-integrable thermal IR spectral imagers. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement