Phase-controlled Optical PT symmetry and asymmetric light diffraction in one- and two-dimensional optical lattices

We propose a novel scheme for asymmetric light diffraction of a weak probe field in a one-dimensional (1D) and two-dimensional (2D) lattice occupied with cold atoms. The atoms are driven into the double-lambda-type configuration by a standing wave, two coupling laser fields and a probe. Our study suggests the proposed scheme is capable of forming an asymmetric diffraction as a result of inducing optical parity-time symmetry in both 1D and 2D lattices. Moreover, it is demonstrated that the asymmetric pattern of diffraction can be dynamically manipulated by means of adjusting the relative phase. Furthermore, it is revealed that in the case of 1D lattice (grating), intensity variation of the coupling fields has a significant impact on the intensity of diffraction orders.