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arXiv · 2510.23592

Coherent all-optical tuning of large-area phase-gradient metasurface

Zhiping He·Xu Fang·Juejun Hu
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Abstract

Tunable active metasurfaces have become a major research focus in recent years. Among tuning mechanisms, all-optical coherent control stands out because it requires no material or geometric change, enabling ultrafast, low-energy, interference-based modulation of amplitude, phase, and polarization in ultrathin devices. However, when applied to phase-gradient metasurfaces, coherent control has been limited to small apertures effectively confined to a single Fresnel zone, leading to large divergence and degraded beam quality. Here we propose and numerically validate a scalable method that enables large-area coherent control. The key idea is to use coherent illumination to tune the phase gradient within each Fresnel zone while a direct search algorithm optimizes zone-by-zone parameters to meet system-level targets. Using this principle, we demonstrate continuous tuning of a large-area metasurface for continuous beam-steering without per-meta-atom phase actuation. The same framework applies broadly to continuously tunable phase-gradient optics, including varifocal metalenses, parfocal zoom metalenses, tunable axicons, and related dynamic focusing elements.

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Zhiping He, Xu Fang, Juejun Hu. 2025-10-27. Coherent all-optical tuning of large-area phase-gradient metasurface. https://doi.org/10.1364/josab.582723

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