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Journal of Physics B Atomic Molecular and Optical Physics

Cavity output field nonreciprocal control via interference effects

Yang Zhang, Yu-Bo Ma, Hongwei Zhu, Chang‐shui Yu

Published Mar 15, 2024• 2 citations
Publisher

Abstract

Abstract We propose a scheme to investigate the coherent control of the output field in an asymmetrical cavity with and without atom interaction. We show that the system displays the phenomenon of nonreciprocal opacity and that broken cavity spatial symmetry is the sufficient and necessary condition to achieve nonreciprocal opacity when the relative phase of the input fields vanishes. Moreover, we also include the effect of the relative phase produced by the incoming fields and show how it realizes and modifies the nonreciprocal opacity in a symmetrical cavity. As a key result, we find that either the participation of atom–cavity interaction or the relative phase can promote the nonreciprocal opacity into a wider operating regime. Our findings show that, although nonreciprocal opacity is analogous to the optical diode effect and our system behaves like an optical isolator, it can still be operated in both forward and backward directions simultaneously.

DOI
10.1088/1361-6455/ad34a1

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Abstract We propose a scheme to investigate the coherent control of the output field in an asymmetrical cavity with and without atom interaction. We show that the system displays the phenomenon of nonreciprocal opacity and that broken cavity spatial symmetry is the sufficient and necessary condition to achieve nonreciprocal opacity when the relative phase of the input fields vanishes. Moreover, we also include the effect of the relative phase produced by the incoming fields and show how it realizes and modifies the nonreciprocal opacity in a symmetrical cavity. As a key result, we find that either the participation of atom–cavity interaction or the relative phase can promote the nonreciprocal opacity into a wider operating regime. Our findings show that, although nonreciprocal opacity is analogous to the optical diode effect and our system behaves like an optical isolator, it can still be operated in both forward and backward directions simultaneously.
We present a work of promoted optical nonreciprocity (ONR) in an asymmetrical cavity containing two asymmetrically arranged two-level atoms with a weak atom-atom interaction. The input-output relation is worked out by using a perturbative approach. Results show that the bistable-monostable-bistable phase transition would exist when the second atom is present, where the optical bistability and nonreciprocity change considerably. Contributions of two types of spatial asymmetries suggest that the ONR originates from the cooperation of the cavity spatial symmetry breaking and the optical nonlinearity, regardless of the atomic spatial symmetry breaking. In addition to the experimentally proved bistable ONR, a type of monostable ONR is proposed, which operates in the monostable phase. Both the ONR optimal regime and the block rate are boosted by adding the other atom in the cavity. Our findings suggest a prospective approach to the generation of a giant ONR by two atoms with unequal atom-cavity coupling strengths.
We propose a scheme to realize tunable and strong nonreciprocal photon blockade (PB) in an asymmetric Fabry-Pérot cavity. The setup consists of a single-mode optical cavity trapping a two-level atom, with the cavity coherently driven by a laser and the atom pumped by an auxiliary control field of the same frequency. By engineering quantum interference between multiple excitation pathways by adjusting the amplitude and relative phase of the control laser, we identify two distinct optimal control conditions that enable directional suppression of two-photon states. Under optimal control conditions, strong nonreciprocal PB is achieved, with a nonreciprocal ratio exceeding 30 dB over a broad operational bandwidth. The proposed protocol requires only standard coherent laser sources and is compatible with current cavity QED experimental setups, offering a practical and scalable platform for nonreciprocal quantum photonics.
We improve the nonreciprocal unconventional photon blockade (UCPB) in an asymmetrical single-mode cavity with two asymmetrical arranged two-level atoms (TLAs) where cavity and atom spatial symmetry breakings are involved in. In order to get direction-dependent UCPB in asymmetrical system, we deduce two restrictions of frequency and intensity through the steady solution of the cavity QED system analytically. The former restriction is exactly the same as that of a single-atom case, and the latter restriction combined with both spatial asymmetries. Controllable UCPB in this model shows an improving nonreciprocal UCPB with wider operating regime which is promoted by two asymmetrical arranged atoms. The most innovation of this work is that the contributions of two spatial symmetry breakings are figured out clearly and they play different roles in nonreciprocal UCPB. The cavity spatial symmetry breaking and weak nonlinearity are essential to quantum nonreciprocity, while the atoms spatial symmetry is not and it only can promote such nonreciprocal UCPB. Our findings show a prospective access to manipulate quantum nonreciprocity by a couple of atoms.
We investigate the optical bistability behavior of a two-sided cavity quantum electrodynamics system. The nonlinear input–output relation of the atom–cavity system coupled by two input light fields from two ends of the cavity can be controlled by a control light from the free space. Different from the common optical bistability phenomenon in the atom–cavity system, two separate bistability regions are observed. The bistability threshold and hysteresis loop can be well controlled by the control light. Because of field interference, the output light intensity becomes different with varying the relative phase of two incident fields. The output field intensity at the threshold of the first bistability region approaches zero with either increasing the detuning or lowering the intensity of the control light; thus, the perfect photon absorption condition is extended and a broadband near-perfect photon absorber is realized. Furthermore, we show an asymmetrical transmission feature due to field interference.
Abstract A coherent perfect absorption (CPA) scheme is theoretically analyzed in a three‐cavity system comprising two linear cavities and an auxiliary cavity. On account of the quantum interference stemming from the presence of the coupled auxiliary cavity, CPA can be realized by appropriately tuning system parameters. It is also demonstrated that coupling to the auxiliary cavity is the necessary and sufficient condition for the system to exhibit CPA behavior. Furthermore, by adjusting the relative phase between the input fields, asymmetric destructive interference occurs between the two cavity sides. Consequently, the output field intensity, which depends on the relative phase, can be utilized to achieve nonreciprocal opacity. The results may provide a purely optical platform for application in the development of photon control.
Optical bistability of a single-mode cavity containing a two-level atom in the Purcell regime has been analyzed. Compared with the case of a symmetric cavity, we find that the bistable regime of input power in an asymmetric cavity can be controlled by adjusting the cavity-loss rates of the asymmetric walls. Such results provide an optimal window of input power to realize giant optical nonreciprocity, which has promising application as the smallest all-optical diode unit with low operation power and high transmitted contrast.