High-resolution angle-interrogated optical spectrometry enabled by nonlocal metasurfaces

Chip-scale spectrometers promise to compress bench-top systems to millimeter-scale footprints, unlocking applications in wearable health monitoring and the IoT. However, the prevailing paradigm based on optical metasurfaces still trades spectral resolution for pixel count: higher resolving power or broader bandwidth demands denser pixels, larger metasurface areas, tighter lithographic tolerance, and higher cost. Here we eliminate this trade-off by employing a single, all-dielectric, nonlocal metasurface optimized for high spectral contrast. By meticulously engineering the thickness and duty cycle of the unit cell, we suppress the non-resonant background transmission while hosting high-Q quasi-guided modes (QGMs) with strong angular dispersion. Each incident angle excites only one narrow resonance wavelength; sweeping the angle therefore maps the full spectrum onto a single-pixel transmission trace-no pixel array, no reconstruction algorithm, and no dispersive optics are required. The resolution is defined jointly by the quality factors (Q-factor) of the QGM and the angular step size. Experimentally, we demonstrate high-resolution across the 1458-1525 nm window on a 1 mm², transmission-only device that needs no calibration beyond angle encoding and no post-processing beyond peak finding. The approach is foundry-compatible and offers a low-cost, high-precision route to field-deployable spectroscopy.