Antireflection by design in bilayer metasurfaces
Abstract
Antireflection coatings are ubiquitous in optical systems, where they maximize transmission and suppress undesirable reflections by impedance-matching uniform interfaces. Extending this principle to metasurfaces, however, is fundamentally more challenging because wavefront control requires a library of geometrically distinct meta-atoms, each locally imposing a prescribed phase that is tethered to its transmittance. Here, we show that vertical integration resolves this constraint by allowing bilayer meta-atoms to operate simultaneously as a phase shifter and an impedance-matching stack. Using an effective thin-film model, we derive a design rule that links the effective indices of two independently patterned layers and identifies antireflective bilayer libraries with full - transmission-phase coverage. We realize this concept in a free-standing TiO/TiO metalens operating at 1310 nm, which suppresses reflectance below that of bare glass while preserving diffraction-limited focusing. These results establish bilayer metasurfaces as a framework for co-engineering optical impedance and wavefront response at the meta-atom level.
Cite
@article{arxiv.2605.19970,
title = {Antireflection by design in bilayer metasurfaces},
author = {Jaewon Oh and Davide Cassara and Alfonso Palmieri and Lorenzo Piatti and Janderson Rocha Rodrigues and Ahmed H. Dorrah and Paulo Dainese and Federico Capasso},
journal= {arXiv preprint arXiv:2605.19970},
year = {2026}
}