Spatial phase controlled symmetric and asymmetric photoinduced lattice in an atomic ensemble

Two-dimensional (2D) photoinduced lattices in atomic ensembles constitute an ideal platform for the systematic investigation of light−matter interactions and controllable diffraction phenomena. Nevertheless, existing research efforts have primarily concentrated on fixed or symmetric lattice configurations, resulting in insufficient exploration of asymmetric diffraction behaviors. Herein, we theoretically propose a 2D phase-controllable photoinduced lattice, which is constructed by overlapping two identical sublattices with independently tunable spatial phases within an atomic ensemble. Spatial phase difference between the two sublattices can be controlled directly by tuning the initial phase of the lattice-forming beams, eliminating the need for complex optical path designs and tedious system optimization. We demonstrate that the absorption, dispersion, and transmission properties of the proposed lattice can be dynamically tuned via photon detuning, leading to the generation of both amplitude- and phase-type lattices. Notably, the amplitude-type lattices exhibit insensitivity to phase variations, whereas the phase-type lattices demonstrate remarkable phase-dependent energy transfer effects and pronounced directional asymmetry. Specifically, a one-dimensional (1D) spatial phase difference between the two identical sublattices induces stripe-like modulation, whereas a 2D spatial phase difference yields reconfigurable anisotropic 2D modulation patterns. Furthermore, we demonstrate that the combined modulation of detuning and spatial phase difference induces periodic asymmetric oscillations in diffraction energy, enabling precisely controllable asymmetric distribution of diffraction. Our work establishes a comprehensive theoretical framework for phase-driven asymmetric diffraction in photoinduced lattices and provides an effective strategy for the development of dynamically reconfigurable all-optical nonreciprocal photonic devices.