Antireflection by design in bilayer metasurfaces

Jaewon Oh; Davide Cassara; Alfonso Palmieri; Lorenzo Piatti; Janderson Rocha Rodrigues; Ahmed H. Dorrah; Paulo Dainese; Federico Capasso

arXiv · 2605.19970

Antireflection by design in bilayer metasurfaces

Jaewon Oh·Davide Cassara·Alfonso Palmieri·Lorenzo Piatti·Janderson Rocha Rodrigues·Ahmed H. Dorrah·Paulo Dainese·Federico Capasso

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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 $0$-$2\pi$ transmission-phase coverage. We realize this concept in a free-standing TiO$_2$/TiO$_2$ 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.

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Jaewon Oh, Davide Cassara, Alfonso Palmieri, Lorenzo Piatti, Janderson Rocha Rodrigues, Ahmed H. Dorrah, Paulo Dainese, Federico Capasso. 2026-05-19. Antireflection by design in bilayer metasurfaces. https://arxiv.org/abs/2605.19970

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