Single-Layer Vector Vortex Metalens for Direction-Selective Edge Detection

Edge detection is a fundamental operation for data compression, feature recognition, and structural analysis, underpinning a wide range of scientific and technological applications. Despite recent advances, most optical analogue edge detection methods based on compact metalenses suffer from a lack of tunable directional selectivity, posing challenges for their deployment in real-world scenarios. Here, we present a compact vector vortex metalens composed of a single-layer silicon carbide metasurface for real-time, broadband, direction-selective edge detection. By engineering the superposition of spin-dependent vortex and antivortex beams, the metalens generates a point spread function with radially varying polarization states. Directional edge features are selectively extracted by introducing a linear analyzer after the metalens without requiring external Fourier optics or computational reconstruction. This directional selectivity offers the key advantage of effectively eliminating directional defects in the observed objects, which allows the contours of the objects to be better identified. We experimentally demonstrate high-resolution edge detection across a broadband spectrum for both amplitude-type and phase-type objects such as biological samples. This approach offers an ultrathin and integrable solution for next-generation optical systems that demand real-time orientation-dependent feature analysis within a minimal footprint.