Subwavelength van der Waals GeSe arrays for enhanced weak-light polarization photodetection

Polarization-resolved weak-light photodetectors, capable of extracting intensity, polarization degree, and phase retardation, are essential for robust perception and feature identification in complex environments. Low-dimensional semiconductors are attractive for weak-light sensing with ultrathin geometry enabling efficient photocarrier modulation, whereas in-plane anisotropic van der Waals (vdW) crystals provide intrinsic polarization selectivity without external polarizers. However, practical devices typically suffer from limited photon utilization, insufficient signal-to-noise ratio (SNR), and modest polarization ratio, making it difficult to simultaneously achieve high polarization contrast and reliable operation under ultralow illumination. Here, we develop a subwavelength array (SWA) strategy for in-plane anisotropic vdW GeSe, where the nanowire array geometry is co-designed with the low-symmetric direction of GeSe (armchair axis) to synergistically enhance photon harvesting and anisotropic photoresponse. By optimizing the nanowire width and array periodicity, the local electromagnetic-field enhancement is efficiently activated. Notably, the array architecture expands the dynamic response to 144 dB under 808 nm excitation and extends the detectable white-light regime down to starlight-level (0.1 lx), together with integrating machine-learning-assisted analysis of weak-light images. We establish vdW GeSe SWA arrays as an integration-friendly route to concurrently enhance weak-light SNR, enabling high-resolution polarized imaging and intelligent in-sensor vision.