We present a dual-gate optical transistor based on a multimode optomechanical system, composed of three indirectly coupled cavities and an intermediate mechanical resonator pumped by a frequency-matched field. In this system, two cavities driven on the red mechanical sidebands are regarded as input/ouput gates/poles and the third one on the blue sideband as a basic/control gate/pole, while the resonator as the other basic/control gate/pole. As a nonreciprocal scheme, the significant unidirectional amplification can be resulted by controlling the two control gates/poles. In particular, the nonreciprocal direction of the optical amplification/rectification can be controlled by adjusting the phase differences between two red-sideband driving fields (the pumping and probe fields). Meanwhile, the narrow window that can be analyzed by the effective mechanical damping rate, arises from the extra blue-sideband cavity. Moreover, the tunable slow/fast light effect can be observed, i.e, the group velocity of the unidirectional transmission can be controlled, and thus the switching scheme of slow/fast light effect can also utilized to realize both slow and fast lights through opposite propagation directions, respectively. Such an amplification transistor scheme of controllable amplitude, direction and velocity may imply exciting opportunities for potential applications in photon networks and quantum information processing.

We study the optical response of a double optomechanical cavity system assisted by two Rydberg atoms. The target atom is only coupled with one side cavity by a single cavity mode, and gate one is outside the cavities. It has been realized that a long-range manipulation of optical properties of a hybrid system, by controlling the Rydberg atom decoupled with the optomechanical cavity. Switching on the coupling between atoms and cavity mode, the original spatial inversion symmetry of the double cavity structure has been broken. Combining the controllable optical non-reciprocity with the coherent perfect absorption/transmission/synthesis effect (CPA/CPT/CPS reported by [ X.-B. YanOpt. Express 22, 4886 (2014)], we put forward the theoretical schemes of an all-optical transistor which contains functions such as a controllable diode, rectifier, and amplifier by controlling a single gate photon.

We study the steady optical responses of a cold atomic ensemble driven into the three-level ladder configuration involving a Rydberg state at finite temperatures. By improving the superatom model with thermal movement included, we calculate relevant atomic coherence effects and find that the residual Doppler broadening at the mK–K temperatures will weaken the nonclassical properties of transmitted probe photons. Furthermore, propagation directions of the probe and coupling fields have a great influence on various properties related to electromagnetically induced transparency. That is, the residual Doppler effect is more destructive to relevant atomic coherence effects in the co-propagation case but can be partially eliminated in the counter-propagation case.

We propose a theoretical scheme in a cold rubidium-87 (⁸⁷Rb) atomic ensemble with a non-Hermitian optical structure, in which a lopsided optical diffraction grating can be realized just with the combination of single spatially periodic modulation and loop-phase. Parity-time (PT) symmetric and parity-time antisymmetric (APT) modulation can be switched by adjusting different relative phases of the applied beams. Both PT symmetry and PT antisymmetry in our system are robust to the amplitudes of coupling fields, which allows optical response to be modulated precisely without symmetry breaking. Our scheme shows some nontrivial optical properties, such as lopsided diffraction, single-order diffraction, asymmetric Dammam-like diffraction, etc. Our work will benefit the development of versatile non-Hermitian/asymmetric optical devices.

Phase gratings, each period of which consists of even numbers of equal-width and equal-thickness elements, can be devised to attain asymmetric diffraction patterns. We show that engineering of offset refractive indices in different elements exhibiting a spatially odd symmetry leads to the elimination of a single diffraction order (directional elimination), while further manipulations on offset refractive indices may lead to the elimination of all odd or even orders (grouped elimination) or all orders but one or two selected (directional selection). These intriguing effects arise from destructive interference between diffracted amplitudes contributed by paired or successive elements, and violation of Friedel's law in such transparent gratings is an effect of higher order multiple scattering.

We investigate the light propagation dynamics in ultra-cold Rydberg medium with inverted-Y configuration based on the superatom theory. It is viable to store light information in two types of atomic spin coherence (trivial spin coherence and Rydberg spin coherence), which makes the system a prospective platform for versatile light manipulation. A normal feature is to realize efficient light storage with simultaneous resonant control fields applied. An intriguing feature is to split light into two beams with different intensities and statistical properties if the control fields are applied separately. The beam of light retrieved from the Rydberg spin coherence is severely attenuated and shows anti-bunching character accompanied by the cooperative optical nonlinearity. Moreover, generation and manipulation of beating signal are achievable by applying the non-resonant control fields.