Wavelength-Scale Nonlocal Metadevices for Light Trapping and Vector Beam Emitting

Nonlocal metasurfaces harness the physics of bound states in the continuum (BICs) to enable efficient light trapping and mode multiplexing. By engineering strong interatom interactions, the radiation channels can be suppressed, supporting high-quality (Q) factor modes. However, in practical structures, the finite-size-induced radiative loss at the boundaries limits the achievable Q factor and hinders applications. Here, we eliminate laterally radiative channels by bending the nonlocal metasurface into a continuous boundary to realize a nonlocal metadevice, overcoming the Q limit of finite size and obtaining highly efficient light trapping. We experimentally demonstrate that, at the wavelength scale, the Q factor approaches 10⁵, comparable to that of the one-dimensional infinite quasi-BIC. Moreover, we realize the generation of multiple vector beams from nonlocal metadevices. This work provides a pathway toward integrating nonlocal metadevices with on-chip photonics.