Detecting and controlling the chirality of matter play an essential role in exploring nature, providing previously unexplored avenues for matter discrimination and quantum manipulation. In such tasks, chiral probes are essential in defining or enhancing the chiral dichroism response. However, overlooking their influence on the symmetry of the medium hampers the ability to deterministically induce electromagnetic chirality. Here, we propose a simple yet versatile all-optical chirality transfer method to generate and manipulate the electromagnetic chirality of a neutral atomic medium. By inducing chirality-dependent dispersion in the atomic system, our method enables deterministic and tunable control of chirality transfer via a helical field. We theoretically analyze the mechanism of this optically induced symmetry breaking and experimentally demonstrate the helicity-dependent response of the medium. Our results show that the induced chirality can be effectively suppressed or enhanced, enabling deterministic electromagnetic enantioselection. This approach opens an efficient pathway for manipulating chiral symmetry breaking in light-matter interactions.
Detecting and controlling the chirality of matter play an essential role in exploring nature, providing previously unexplored avenues for matter discrimination and quantum manipulation. In such tasks, chiral probes are essential in defining or enhancing the chiral dichroism response. However, overlooking their influence on the symmetry of the medium hampers the ability to deterministically induce electromagnetic chirality. Here, we propose a simple yet versatile all-optical chirality transfer method to generate and manipulate the electromagnetic chirality of a neutral atomic medium. By inducing chirality-dependent dispersion in the atomic system, our method enables deterministic and tunable control of chirality transfer via a helical field. We theoretically analyze the mechanism of this optically induced symmetry breaking and experimentally demonstrate the helicity-dependent response of the medium. Our results show that the induced chirality can be effectively suppressed or enhanced, enabling deterministic electromagnetic enantioselection. This approach opens an efficient pathway for manipulating chiral symmetry breaking in light-matter interactions.
Detecting and controlling the chirality of materials play an essential role in exploring nature, providing new avenues for material creation, discrimination, and manipulation. In such tasks, chiral reagents are essential in defining or enhancing the chiral dichroism response. However, ignoring their influences on the symmetry of the medium hamper the ability to control and induce asymmetric synthesis. Here, we propose a simple but versatile chirality transfer method for synthesizing and manipulating the chirality of medium. The proposed method induces the dispersion of light in a neutral atomic system, allowing to deterministically and tunably control the chirality transfer using a helical field. First, we theoretically analyze the mechanism for this optically induced chirality transfer. Afterwards, we experimentally study the enantio-sensitive feature of the medium exposed to the auxiliary chiral field. This result can be suppressed or enhanced in a deterministic enantio-selection, opening up an efficient way to manipulate asymmetric synthesis.
Chirality has been extensively studied for well over a century, and its potential applications range from optics to chemistry, medicine, and biology. Ingenious experiments have been designed to measure this naturally small effect. Here we discuss the possibility of producing a medium having a large chiral effect by using the ideas of coherent control. The coherent fields resonant with appropriate transitions in atomic or molecular systems can be used to manipulate the optical properties of a medium. We demonstrate experimentally very large magnetochiral anisotropy by using electromagnetic fields in atomic Rb vapors.
We demonstrate that light propagation in reciprocal chiral photonic media admits a unified description in terms of an emergent Dirac structure in helicity space. Starting from Maxwell's equations, we reformulate the electromagnetic field as a four-component spinor governed by an effective non-Hermitian optical Dirac equation. In this representation, the magnetoelectric response of the chiral medium appears as a helicity-dependent background that modifies the spectrum and eigenmodes, while the breaking of the spin-degenerate condition generates the intrinsic spin-orbit coupling between helicity and orbital degrees of freedom. After projection onto the positive-frequency sector, the theory reduces to an exact two-level helicity-orbital model. This model is found to have an analytical solution and describes coherent Rabi-like oscillations between spin-orbit-coupled vector modes. Chirality controls the helicity splitting and detuning, whereas the electromagnetic mismatch of the medium determines the coupling strength responsible for oscillatory spin-orbit conversion. The resulting dynamics is constrained by exact conservation of the total angular momentum, leading to reversible conversion between spin and orbital angular momentum with well-defined selection rules. Our work establishes an optical Dirac framework for structured light in chiral media, and provides experimentally accessible predictions for chirality-controlled oscillations, polarization dynamics, and orbital angular momentum conversion in structured optical fields.
Birefringence and dichroism in atomic systems are active areas of research. Circular dichroism is typically observed in chiral atoms, molecules (such as DNA), and optically asymmetric materials. These phenomena enable polarization-based selectivity and high-precision measurements with applications in optical systems, biomedical diagnostics, and advanced photonics.Meanwhile, negative refractive index materials offer exotic applications in optics and photonics, including super-resolution imaging, invisibility cloaking, and sub-wavelength imaging. Here, we identify a novel route to achieving birefringence and dichroism in a left-handed system for the first time.We investigate the optical activity of an atomic left-handed medium, analyzing the interaction of left- and right-circularly polarized light with different atomic states while incorporating local field corrections. Notably, our results demonstrate simultaneous left-handedness for both polarization states. Furthermore, we find that electric birefringence and dichroism are significantly enhanced with increasing control field strength, while magnetic birefringence and dichroism can be fully controlled via strong laser coupling.These findings have promising implications for spintronics, image transmission in metamaterials, and the development of optical switches and high-speed data transmission devices, opening new avenues in quantum optics and photonics.
Chiral light-matter interactions lie at the heart of emerging technologies such as quantum network protocols and quantum logic gates. In the few photon regime, it has been shown that chiral interactions between photons and a waveguide-embedded two-level quantum emitter can break reciprocity and impart a directional π phase shift while the transmission remains intact. In this work, we present a model for multicolor, chiral nonlinear interactions in waveguides using a Green's Tensor formalism. We challenge previously held notions and demonstrate the complex photon dynamics hidden in multicolor light-matter interactions in the few photon regime. By modulating a stronger control beam, we can manipulate a weaker signal beam that contains much less than a single photon per emitter lifetime, on average. We develop equations for the transmission of the signal photons and removing the control photons to uncover the true strength of these nonlinearities, which we show is stronger than what is possible in symmetric geometries. The model predicts tunable unity extinction and up to 30% amplification in the signal, a $\sim100xincreasefromstandardpredictionsinwhichcontrolphotonsarepresent.Wealsopredictatunable0−π$ phase shift via control modulation with significant robustness to emitter imperfections. Our model opens a new regime of directional nonlinear quantum light-matter interactions for study, providing a route to efficient all-optical control of photons.
Structured light offers a powerful approach to tailor light--matter interactions in quantum systems with chiral properties. While chirality has been extensively studied in passive platforms, the role of optical gain in controlling chiral quantum dynamics remains largely unexplored. In this work, we develop a general theoretical framework to describe the dynamics of an atomic system interacting with structured gain environments, where amplification depends on the light's polarization or momentum. By quantizing the electromagnetic field in linear bianisotropic media with gain and extending the Lindblad formalism to these settings, we derive a master equation governing the atom's irreversible evolution. We show that chiral gain can break time-reversal symmetry and drive the system toward a symmetry-broken steady state with nonreciprocal properties. This effect is illustrated in detail for moving plasmonic substrates, which exhibit inherently chiral gain that selectively amplifies transitions of a given handedness. Our results establish chiral gain as a novel mechanism for engineering nonreciprocal quantum steady states.