Gradient-Metasurface-Contact Photodetector for Visible-to-Near-Infrared Spin Light

Spin light detection is a rapidly advancing field with significant impact on diverse applications in biology, medicine, and photonics. Developing integrated circularly polarized light (CPL) detectors is pivotal for next-generation compact polarimeters. However, previous compact CPL detectors, based on natural materials or artificial resonant nanostructures, exhibit intrinsically weak CPL polarization sensitivity, are susceptible to other polarization states, and suffer from limited bandwidths. A gradient-metasurface-contact CPL photodetector is demonstrated operating at zero-bias with a high discrimination ratio (≈1.6 ✗ 10⁴), broadband response (500-1100 nm), and immunity to non-CPL field components. The photodetector integrates InSe flakes with CPL-selective metasurface contacts, forming an asymmetric junction interface driven by CPL-dependent unidirectional propagating surface plasmon waves, generating zero-bias vectorial photocurrents. Furthermore, it is implemented the developed CPL photodetector in a multivalued logic system and demonstrated the optical decoding of CPL-encrypted communication signals. This metasurface contact engineering represents a new paradigm in light property detection, paving the way for future integrated optoelectronic systems for on-chip polarization detection.