Metasurface dispersion engineering for wavelength-insensitive directional photodetection

Recent work has established the promise of tailoring the angular response of photodetectors through the integration of gradient metasurfaces on their illumination window for multiple applications in computational imaging. These metasurfaces function as reciprocal-space filters enabling the selective detection of light incident along a small, geometrically tunable set of directions. Here, we describe their development for wavelength-insensitive operation. The key outcome is a near-infrared device featuring a sharp peak in its measured angular response with minimal variations in center angle (<1° standard deviation) and peak value (<1.5 dB) across a bandwidth of 150 nm, nearly 3 times broader than in previously reported metasurface directional photodetectors. These results demonstrate the suitability of this device technology for applications involving LED light or even natural illumination combined with broadband spectral filters.