Arrangement-Dependent Photon Pair Generation in 2D Arrays of Nonlinear Emitters

Nonlinear metasurfaces have recently emerged as subwavelength-thin sources of photon pairs with complex quantum states [1]. Although metasurfaces are specially known for their capabilities in manipulating the properties of light, these capabilities have not yet been explored in depth for controlling photon-pair generation. In this work, we study photon-pair generation by a nonlinear metasurface, focusing on effects that arise from a periodic or disordered arrangement of the meta-atoms. We also find a special detection configuration, where the two-photon directionality pattern is independent of the meta-atom arrangement and even robust to disorder. The symmetry in the physics of two-photon interference is identified as the cause of such an effect.