The diffraction pattern of a two-dimensional optically induced atomic lattice is reported experimentally in a three-level atomic system. Such a two-dimensional optical lattice is established by two orthogonal standing-wave fields induced by the interference of two pairs of coupling laser beams. When the probe beam is launched into it, a spatially modulated discrete diffraction pattern can be obtained at the output plane of the vapor cell under the electromagnetically induced transparency condition. We investigate the diffraction pattern under different experimental parameters and find that it can be effectively controlled by tuning the coupling laser power and two-photon detuning. Our work may potentially pave the way for studying the control of light and other intriguing physical phenomena based on such a periodically modulated atomic lattice.

A novel tunable all-optical grating is realized experimentally in a V + Ξ configuration coherent rubidium thermal vapor. This new energy level structure employs a Rydberg level as the uppermost level and contains two typical electromagnetically induced transparency energy level configurations with the same probe field. Compared with the traditional V-type three-level grating, a significant improvement of the diffraction efficiency of this novel grating was observed. Its improvement was then also demonstrated experimentally by the transition spectrum and theoretically by a comprehensive simulation. The diffraction efficiency gain introduced by the control laser field was tuned with several experimental parameters, such as the atomic density and the control field intensity. And the maximum enhancement rate of first-order diffraction efficiency is proved to be as high as 30%. Such a novel all-optical tunable grating promises to be the new driving force in the advancement of all-optical communications and information technology.

We present a Rydberg atom-based receiver with amplitude modulation (AM) technique for the fifth-generation (5G) millimeter-wave wireless communication in a five-level ${^{85}}$Rb atomic coherent system. The carrier microwave (C-MW) field at frequency of 24.12 GHz, corresponding to the 5G millimeter-wave wireless communication band, is encoded by AM technique, and then decoded by Rydberg atom-based receiver with the assistance of an auxiliary microwave (A-MW) field. An atomic response to the C-MW field linking to the signal-noise-ratio (SNR) of decoded signal, which plays a prerequisite role in 5G millimeter-wave wireless communication with large data transfer capacity, is obtained by investigating the optimal powers of probe laser, coupling laser, and A-MW field. Also, an appropriate AM frequency of 10 kHz, which has an influence on the data transfer capacity, is acquired with 54 dB SNR of decoded signal. Under the above experimental conditions, the maximum data transfer capacity of 82.5 kbit/s is achieved when the C-MW field power tends to saturate. The bandwidth of Rydberg atom-based receiver is determined as 3.5 GHz, and the instantaneous bandwidth is approximately 106.3 kHz. As a result, 5G signals on three waveforms are transferred with high fidelity, frequency recovery rate, and time synchronization to verify the performance of this receiver for an actual communication. This scheme provides an effective approach for realizing 5G millimeter-wave wireless communication with wide bandwidth, large data transfer capacity, and high fidelity.

Optical vortex arrays (OVAs) containing multiple vortices have been in demand for multi-channel optical communications and multiple-particle trapping. In this Letter, an OVA with tunable intensity and spatial distribution was implemented all-optically in a two-dimensional (2D) electromagnetically induced atomic lattice (EIL). Such a square lattice is constructed by two orthogonal standing-wave fields in 85 R b vapor, resulting in the periodically modulated susceptibility of the probe beam based on electromagnetically induced transparency (EIT). An OVA with dark-hollow intensity distribution based on 2D EIL was observed in the experiment first. This work thus studied the nonlinear 2D EIL process both theoretically and experimentally, presenting, to the best of our knowledge, a novel method of dynamically obtaining and controlling an OVA and further promoting the construction of all-optical networks with atomic ensembles.