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Optics Letters

Angle- and field-tunable unidirectional zero reflection in an asymmetric single-defect atomic lattice

Chen Peng, Duanfu Chen, Huang Hongbin, Hong Chun Yang

Published Aug 19, 2026• 0 citations
Publisher

Abstract

Based on spatial symmetry breaking, we propose a tunable unidirectional zero-reflection scheme in a one-dimensional single-defect atomic lattice. Reflection suppression stems from destructive interference between the direct-reflection and multiple-scattering components, whose amplitudes and phases are co-modulated by coherent atomic response, Bragg scattering, and structural asymmetry. The system supports both broadband and narrowband asymmetric-reflection regions, each containing a unidirectional zero-reflection point, with the minimum reflectivity reaching below 10 −6 in one incident direction while remaining above 0.93 in the reverse direction. External coherent fields tune the UZR frequency, and the vacant-region length modulates phase and scattering amplitudes for zero-reflection at discrete incident angles. Boasting robustness against atom number density fluctuations, this work provides an intuitive theoretical framework for directional scattering, promising tunable optical switches, low-back-reflection photonic structures, and asymmetric light-control devices.

DOI
10.1364/ol.612724

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Based on spatial symmetry breaking, we propose a tunable unidirectional zero-reflection scheme in a one-dimensional single-defect atomic lattice. Reflection suppression stems from destructive interference between the direct-reflection and multiple-scattering components, whose amplitudes and phases are co-modulated by coherent atomic response, Bragg scattering, and structural asymmetry. The system supports both broadband and narrowband asymmetric-reflection regions, each containing a unidirectional zero-reflection point, with the minimum reflectivity reaching below 10 −6 in one incident direction while remaining above 0.93 in the reverse direction. External coherent fields tune the UZR frequency, and the vacant-region length modulates phase and scattering amplitudes for zero-reflection at discrete incident angles. Boasting robustness against atom number density fluctuations, this work provides an intuitive theoretical framework for directional scattering, promising tunable optical switches, low-back-reflection photonic structures, and asymmetric light-control devices.
The novel and ingenious scheme we propose for achieving unidirectional reflection lasing (URL) involves integrating a one-dimensional (1D) defective atomic lattice with a coherent gain atomic system. Its physical essence lies in the fact that the right-side reflectivity is drastically reduced due to the destructive interference between primary and secondary reflections, whereas on the left-side primary reflection is effectively suppressed and the secondary reflection is efficiently enhanced, ultimately reaching the lasing threshold. Through numerical results and further analyses, we have elucidated how to precisely tailor the lattice parameters and coupling fields to control destructive interference point (DIP), thereby realizing URL and enabling its active modulation. Our scheme is experimentally feasible and not only effectively circumvents the stringent conditions faced in directly realizing URL, providing a new pathway, but also beneficial for integrating active photonic devices into compact quantum networks and may improve the efficiency of optical information transmission.
Unidirectional lasing is highly desirable for practical high-performance quantum information processing platforms, while most existing schemes still rely on the combination of resonant cavities and nonreciprocal mechanisms. Here, we propose a cavity-free scheme for achieving the onset of narrowband unidirectional reflection lasing (URL) in a single physical system by introducing a coherent gain atomic medium into a one-dimensional defective atomic lattice, where the former amplifies the probe field and the latter provides spatial symmetry breaking and a distributed-feedback mechanism. We show that the threshold condition for URL, characterized by λ + −1 ≃ λ − −1 →0, can be tuned from single-mode to dual-mode by varying the microwave field and the lattice structure. Its underlying mechanism lies in the constructive or destructive interference between the reflections from both sides under distinct Bragg conditions.
We propose an efficient scheme for achieving mode-tunable unidirectional reflection lasing (URL) by establishing a coherent gain atomic system to amplify the probe field and ingeniously designing a one-dimensional (1D) defective atomic lattice. This lattice not only replaces the resonant cavity to provide a distributed feedback mechanism but also breaks the spatial symmetry of the probe susceptibility. Correspondingly, the URL can be characterized by a non-Hermitian degenerate spectral singularity (NHDSS), where the two eigenvalues of the inverse scattering matrix are engineered to satisfy λ S −1 + ≃ λ S −1 − →0. This intriguing NHDSS depends on the probe susceptibility and the Bragg condition, both of which can be modulated by adjusting the external driving fields and lattice structure, rendering the scheme experimentally feasible. Our approach achieves both nonreciprocity and lasing oscillation in a single system, significantly enhancing the efficiency of optical information transmission and facilitating the integration of active photonic devices into compact quantum networks.
Based on the broken spatial symmetry, we propose a scheme for engineering a unidirectional photonic reflector using a one-dimensional atomic lattice with defective cells that have been specifically designed to be vacant. By trapping three-level atoms and driving them into the regime of electromagnetically induced transparency, and through the skillful design of the number and position of vacant cells in the lattice, numerical simulations demonstrate that a broad and high unidirectional reflection region can be realized within the EIT window. This proposed unidirectional reflector scheme provides a new platform for achieving optical nonreciprocity and has potential applications for designing optical circuits and devices of nonreciprocity at extremely low energy levels. Published by the American Physical Society 2024
Coherently manipulating single photons in nanophotonic structures with unidirectional propagation is one of the central goals for integrated quantum information processing. Photonic devices constructed by a single atom coupled to a whispering-gallery-mode microresonator (WGMM) with nonideal chiral photon-atom interactions inevitably induce undesired photon scattering. Here, an external scatterer is introduced to the WGMM to cancel the reflection of signal photons by an atom due to nonideal chiral interactions. By properly tuning the positions of the scatterer, destructive and constructive interferences between reflected photons of different pathways are utilized to control the reflection properties of single incident photons. The results show that the reflection probabilities can be suppressed by applying the interplay between chirality and backscattering. Constructing perfect destructive interferences directly leads to unidirectional propagation even when the photon-atom interactions are not ideal. Because the amplitudes of the reflected photons produced by the scatterer can be enhanced to meet requirements of perfect destructive interfering processes, unidirectional propagation is preserved against dissipations.
For tunable control of asymmetric light reflection, we propose a Rydberg atomic system of the optical response varying in space induced by the long-range position-dependent Rydberg dipole-dipole interaction either in the type of self-van der Waals dipole-dipole interaction or the cross Forster-like dipole-dipole exchange interaction. In such a one-dimensional system consisting of a control atomic driven upon the Rydberg state and a homogeneous target atomic ensemble, the non-localized action from the control atom on the target atoms gradually decreases with the distance between the control and target atoms. Our scheme yields a nonlinear correspondence from a finite spectra range to a finite spatial range of susceptibility via the nonlinear characteristics of Rydberg interaction relative to the position. Therefore, the asymmetric reflection can be induced via the spatial modulation on the target ensemble. In particular, the reflection from one direction can be completely suppressed when the absorption and dispersion parts of the susceptibility are modulated to satisfy the spatial Kramers-Kronig relation in an infinite spectral range. The opposite reflection exhibits a band of a small nonzero reflectivity due to the realistic restriction of the cold atomic density of a relatively small value. Thus, via trapping the target atoms in the optical lattice for the Bragg scattering, we enhance the nonzero reflection obviously and retain the directional reflectionlessness.