On‐Chip Fast Polarization Detection Based on GaAs/Graphene/Black Phosphorus Integrated Photodetectors

On‐chip polarization detection is crucial for applications including imaging, environmental sensing, and optical communications. However, the intrinsic symmetry and multidimensional nature of polarization states, together with weak photoelectric signals, make fast and accurate on‐chip polarization detection highly challenging. Here, we demonstrate rapid polarization detection using GaAs/graphene/black phosphorus (GaAs/Gr/BP) heterostructures. Two detector units‐integrated within a 40 µm × 40 µm footprint and whose black‐phosphorus optical axes are rotated 60° relative to each other‐enable fast, unambiguous linear‐polarization discrimination across the full 0°–180° range. The device exhibits an 8 µs rise time for optical switching and stably identifies polarization signals under a 5 kHz polarization modulation. Meanwhile, the device demonstrates excellent performance characteristics including high light‐to‐dark current ratio (10 6 ), ultra‐low dark current (8 × 10 −12 A), broad spectral response (400–870 nm). With its compact footprint and superior metrics, this photodetector solves the long‐standing challenge of miniaturized, high‐speed polarization‐angle detection and is immediately attractive for on‐chip photonics, high‐resolution polarimetry, and advanced optical communications.