Polarization-Independent Single-Band Guided-Mode Resonance InGaAs Photodetector Array for Snapshot Multispectral Sensing.

Multispectral sensing in the short-wave infrared (SWIR) range is highly desirable for a wide range of applications, from industrial inspection to satellite remote sensing. Here, we report a single-band guided-mode resonance (GMR) InGaAs photodetector (PD) array that enables single-snapshot multispectral sensing through direct readout from each pixel. The device consists of an InGaAs PD with an ultrathin absorption layer bonded onto a Si 2D grating. Although a 2D crossed-grating provides polarization independence, it inherently supports many more optical modes than a 1D grating. To realize a single-band response, we introduce design strategies that suppress higher-order diffraction using a thin grating and eliminate undesired modes by positioning their diffraction angles near the critical angle. The device exhibited a single-band spectral response over a broad wavelength range of 1100-1700 nm, peak responsivities of up to 0.451 A/W, off-peak responsivities below 0.03 A/W, and complete polarization independence. Moreover, a multispectral pixel array can be fabricated using a single patterning step by varying the grating period. We verified the feasibility of snapshot multispectral sensing through area-scan imaging measurements under various input conditions. These results, together with the fabrication simplicity, establish the proposed device as a promising platform for compact, real-time SWIR multispectral sensors.