Polarization-Independent High-Q Phase Gradient Metasurfaces.

Dielectric metasurfaces have emerged as an unprecedented platform for precise wavefront manipulation at subwavelength scales with nearly zero loss. When aiming at dynamic applications such as AR/VR and LiDAR, high-quality factor (high-Q) phase gradient metasurfaces have emerged as a way to boost weak light-material interactions in flat-optical components. However, resonant features are naturally tied to polarization, limiting devices to operating on a single polarization state, which reduces the efficiency and adaptability of wave-shaping. Here, we propose polarization-independent high-Q phase gradient metasurfaces, where two cross-polarized dipolar guided mode resonances (DGMRs) with similar Q around 300 are spectrally aligned while being spatially tuned. Our simulations demonstrate that, by adding less than 5% geometric perturbation, the metasurface can steer arbitrarily polarized beams to 31° with diffraction efficiency >70%. These devices show potential for advancing programmable polarization-independent wavefront shaping and unlocking ways to efficiently sculpt nonlinear frequency generation and mixing processes.