Wavefront engineering with atomic Huygens' surfaces made simple

Abstract

Atomic arrays provide a cooperative platform for light-mediated interactions in nonlocal metasurfaces which can operate in the quantum regime without nanofabricated optical elements or intrinsic material absorption. We present a minimal atomic implementation to harness wavefront engineering and create a near-ideal intrinsic atomic Huygens' surface. A simple bilayer square lattice with a two-atom unit cell, not limited to small lattice spacings, provides near-unity reflectionless transmission and a full $2π$ phase control of transmitted light without the localized site-dependent level shifts of previous proposals. This simplification is achieved through nonlocal radiative excitations that provide the familiar electric-dipole response with even radiation parity as well as an odd-parity radiation channel whose leading multipolar interpretation combines magnetic-dipole and electric-quadrupole contributions in atoms exhibiting only electric dipole transitions. This eliminates the need to simultaneously excite pure electric-dipole and magnetic-dipole responses with exactly matched radiation. We derive a two-mode model for this response and show that it accurately captures full coupled-dipole simulations near the optimal lattice spacings. Because of the wide applicability of coupled-dipole models, the relevance of our microscopic analysis extends beyond atomic physics to nanostructured metasurfaces. Moreover, the same platform also connects directly to established subradiance-protected single-photon storage protocols, suggesting a route toward combining wavefront engineering, storage, and retrieval in a simple atomic bilayer.