High-precision birefringence detection is crucial in many fundamental and applied research fields such as chirality detection, optical clocks and quantum information. Although numerous techniques have been demonstrated to detect birefringence in optical materials, the current detection precision typically remains at 10−8. Here we introduce a different physical mechanism for birefringence detection in the classical regime, achieving an accuracy at the 10−11 level. Our technique uses an effective photonic two-level system, dynamically driven by a birefringence-sensitive synthetic magnetic field created by propagation-invariant spin-orbit-coupled structured light in the subwavelength regime. The magnetic field equivalent induces the Rabi oscillation of photonic state, manifested as a nontrivial periodic spin-orbital angular momentum conversion. The ultrahigh detection precision arises from high-birefringence-sensitive topological transition between different oscillatory modes with high Rabi frequencies. The detection precision is tunable by controlling envelope size of structured light at the subwavelength scale. Our technique benefits a broad range of applications involving optical birefringence. The authors demonstrate that high-precision birefringence detection at the 10−11 level can be achieved using spin-orbit-coupled Rabi oscillations in a photonic two-level system. The presented detection technique benefits a broad range of applications involving optical birefringence such as precise control of the entangled photonic states.
High-precision birefringence detection is crucial in many fundamental and applied research fields such as chirality detection, optical clocks and quantum information. Although numerous techniques have been demonstrated to detect birefringence in optical materials, the current detection precision typically remains at 10−8. Here we introduce a different physical mechanism for birefringence detection in the classical regime, achieving an accuracy at the 10−11 level. Our technique uses an effective photonic two-level system, dynamically driven by a birefringence-sensitive synthetic magnetic field created by propagation-invariant spin-orbit-coupled structured light in the subwavelength regime. The magnetic field equivalent induces the Rabi oscillation of photonic state, manifested as a nontrivial periodic spin-orbital angular momentum conversion. The ultrahigh detection precision arises from high-birefringence-sensitive topological transition between different oscillatory modes with high Rabi frequencies. The detection precision is tunable by controlling envelope size of structured light at the subwavelength scale. Our technique benefits a broad range of applications involving optical birefringence. The authors demonstrate that high-precision birefringence detection at the 10−11 level can be achieved using spin-orbit-coupled Rabi oscillations in a photonic two-level system. The presented detection technique benefits a broad range of applications involving optical birefringence such as precise control of the entangled photonic states.
We present both theoretical and experimental demonstrations of geometric phase (GP) transitions in a synthetic two-level photonic system. We demonstrate the use of this nontrivial phenomenon to achieve an unprecedented birefringence change detection, with a precision up to Δn∼10−11. This result represents a significant improvement of 3 orders of magnitude over conventional techniques (typically limited to the level of Δn∼10−8). In this system, two orthogonal polarizations of light constitute the effective two-level system, which is driven by a birefringence-sensitive synthetic magnetic field. A given photonic spin is able to precess around the “magnetic” field and exhibits a topological transition in its evolution trajectory in parameter space. We establish a direct relationship between the GP transition and birefringence change, which is the basis of our detection technique. This approach significantly improves detection sensitivity and stability as compared with previous detection techniques. Moreover, the presented results benefit many fundamental and applied research fields such as structured light shaping and photonic switching.
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 superresolution imaging, invisibility cloaking, and subwavelength imaging. Here we identify a route to achieving birefringence and dichroism in a left-handed system. 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 in fields at the interface of left-handedness and dichroism.
This study presents an innovative scheme for detecting the orbital angular momentum (OAM) of vortex beams within an atomic ensemble. Leveraging a homogeneously broadened four-level atomic system driven by two orthogonal polarization probe beams, we demonstrate the selective generation of structured beams without the need for magnetic fields between the two ground states. Through detailed theoretical analysis and numerical simulations, we elucidate the phase-dependent behavior of atomic coherences induced by an OAM-carrying Laguerre–Gaussian optical probe beam. These findings enable the creation of petal-like structures within the probe beam, with the number of petals directly correlated to the OAM value. Our investigation underscores the potential of this OAM detection scheme as a highly sensitive and precise sensor, applicable across diverse domains such as telecommunication, microscopy, and optical metrology.
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.
A structured-light-based approach to magneto-optical rotation (MOR) magnetometry is proposed, in which magnetically induced polarization rotation is converted into a directly observable spatial displacement. A radially polarized Laguerre--Gaussian beam propagating through cold 87Rb atoms in the presence of a longitudinal magnetic field experiences circular birefringence, which induces a relative phase shift between the σ+ and σ− polarization components. This phase shift manifests itself as the angular rotation of a petal-shaped interference pattern, enabling the MOR angle to be determined directly from the spatial intensity distribution. Unlike conventional MOR detection techniques based on balanced polarimetry or Stokes-parameter reconstruction, the proposed method requires only a fixed-axis polarization projection and avoids computationally intensive polarization analysis. By translating polarization rotation into a topology-dependent spatial observable, the scheme enables direct and spatially resolved magnetic-field measurements. Furthermore, the use of electromagnetically induced transparency (EIT) allows low-loss operation while preserving high sensitivity. These characteristics make the proposed technique a promising platform for optical magnetometry and structured-light-based quantum sensing.