Abstract We propose a rotation-controlled nonlinear orbital-angular-momentum (OAM) filter based on photonic-band-gap-assisted four-wave mixing (PBG-FWM) in rubidium vapor. The model follows the field convention of PBG-FWM experiments: an OAM probe field
E1 is Bragg-reflected through the nonlinear polarization produced with two counterpropagating Gaussian coupling fields
E3 and
E3′, while the generated field is denoted by
EF. The coupling pair forms a standing-wave Rabi frequency
∣G3s∣2=∣G3∣2+∣G3′∣2+2G3G3′cos(2k3z), which creates the longitudinal PBG modulation and enters the resonant denominator of the third-order susceptibility. Rotation adds an OAM-dependent rotational Doppler shift to the probe and generated FWM modes. In a slow-light PBG-FWM medium this shift is converted into a longitudinal phase-matching perturbation, giving
ηm(Ω)=η0sinc2[Δkrot(m)L/2] in the phase-matching-dominated limit. Rotation can also perturb
χ(3) through Doppler-shifted detunings, producing envelope and asymmetry corrections. The theory predicts OAM-dependent FWM quenching, the readable petal rotation, and a rotationally tunable OAM cutoff. The results provide a design route for rotation-sensitive structured-light processing in atomic nonlinear media.
In the burgeoning field of light-matter interactions, angular momentum has emerged as a pivotal factor, driving innovative research directions. This study delves into the interaction dynamics between vortex lights and an electromagnetically induced transparency (EIT) medium, with a primary focus on elucidating the underlying mechanism of angular momentum transfer. Through comprehensive theoretical analysis and numerical simulations, it is demonstrated that when the probe field carries orbital angular momentum (OAM), the dispersion and absorption characteristics of the EIT medium undergo periodic modulation. This modulation is intricately determined by the azimuthal phase and topological charge of the beam. Notably, the OAM in the driving field exerts no such influence on the medium's properties. Leveraging vortex phase plates (VPPs) or spatial light modulators (SLMs) to manipulate the tunable OAM enables dynamic control over the EIT effect. This breakthrough not only deepens our understanding of light-matter interactions at the quantum level but also unlocks new avenues for high-dimensional quantum information processing and advanced optical communication technologies.
We study the propagation of probe pulses carrying orbital angular momentum (OAM) in a crystal of molecular magnets characterized by a double-$\mathrm{\ensuremath{\Lambda}}$ light-matter coupling scheme. The model is based on the four-wave mixing (FWM) of applied fields interacting with the magnetic dipole moment of the molecular magnets. We consider the light-matter interaction under the situation where a weak probe field carries an optical vortex and investigate the exchange of optical vortices between different frequencies via the FWM in the microwave region. The propagation of OAM beams with nonzero radial indices is then explored. It is found that the conservation of both azimuthal and radial indices is satisfied over the swapping of OAM states of light. Superimposing two initially weak OAM modes with different topological charges creates specific vortex beams with a very characteristic form. The resulting beam contains a central vortex as well as several singly charged peripheral vortices distributed at the same radial distance from the center of the light beam. This complex pattern of vortices arises because the intensity radius of two interfering OAM modes is different. It is shown that the boundary region of intensity dominance of two OAM modes can be controlled by the molecular magnets parameters and strong cw electromagnetic fields. Our proposed scheme may provide a route to study the solid systems suitable for quantum technologies as well as for OAM exchange devices for quantum information processing.
Abstract We show that rotation can strongly amplify the photonic spin Hall effect in a ring Bose–Einstein condensate. For an incident probe beam carrying orbital angular momentum (OAM), the spin-dependent transverse shift of the reflected light is weak in the non-rotating regime but becomes strongly enhanced under rotation because rotation lifts the degeneracy of the condensate mechanical modes via Bragg scattering. The resulting mode splitting produces large photonic spin Hall shifts at ultra-low optical power, with the enhancement increasing with both the condensate winding number L p and the probe OAM l , while remaining weakly affected by atom–atom interactions. Our findings elucidate a rotation-governed mechanism underlying spin-dependent light transport in hybrid atom–optomechanical systems, thereby highlighting its potential for applications in high-precision rotational sensing.
We consider the propagation of slow light with an orbital angular momentum (OAM) in a moving atomic medium. We have derived a general equation of motion and applied it in analyzing propagation of slow light with an OAM in a rotating medium, such as a vortex lattice. We have shown that the OAM of slow light manifests itself in a rotation of the polarization plane of linearly polarized light. To extract a pure rotational phase shift, we suggest to measure a difference in the angle of the polarization plane rotation by two consecutive light beams with opposite OAM. The differential angle $\ensuremath{\Delta}{\ensuremath{\alpha}}_{l}$ is proportional to the rotation frequency of the medium ${\ensuremath{\omega}}_{\text{rot}}$ and the winding number
l of light, and is inversely proportional to the group velocity of light. For slow light the angle $\ensuremath{\Delta}{\ensuremath{\alpha}}_{l}$ should be large enough to be detectable. The effect can be used as a tool for measuring the rotation frequency ${\ensuremath{\omega}}_{\text{rot}}$ of the medium.