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Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)

Amplification and Storage of Orbital Angular Momentum of Light Via Magnetically Assisted Optical Gain

Raoni S. N. Moreira, J. C. de Aquino Carvalho, J. W. R. Tabosa

Published Jun 26, 2023• 0 citations
Publisher

Abstract

Structured light associated with Laguerre-Gauss (LG) modes carrying orbital angular momentum (OAM) is an important tool in many different areas, ranging from optical tweezers to classical and quantum communication systems [1]. In this work we demonstrated the amplification and the storage of light with OAM employing the magnetically assisted gain mechanism. This gain mechanism is based on the manipulation of the dark-state created by a coupling and a probe beam in the Zeeman sublevels of a degenerate two-level system and can provide single-pass optical gain exceeding 100% [2], [3].

DOI
10.1109/cleo/europe-eqec57999.2023.10232461

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Structured light associated with Laguerre-Gauss (LG) modes carrying orbital angular momentum (OAM) is an important tool in many different areas, ranging from optical tweezers to classical and quantum communication systems [1]. In this work we demonstrated the amplification and the storage of light with OAM employing the magnetically assisted gain mechanism. This gain mechanism is based on the manipulation of the dark-state created by a coupling and a probe beam in the Zeeman sublevels of a degenerate two-level system and can provide single-pass optical gain exceeding 100% [2], [3].
Abstract We report on the amplification and the storage of a light vortex beam carrying orbital angular momentum (OAM) in an ensemble of cold cesium atoms in the presence of an external transverse magnetic field. This magnetically assisted optical gain was previously reported in a recent publication and originates from the manipulation of the induced dark state by the external magnetic field. Single pass optical gain exceeding 100 % was measured for beams with different topological charges. Furthermore, we also demonstrate the storage and retrieval of the vortex beams, showing that the amplification and the storage processes preserve the coherent nature of the optical vortex. A simple theoretical model based on density matrix numeric calculation and which accounts for the presence of the external magnetic field was developed and present qualitative agreement with the observed results. Owing to the recent proposal of using light carrying OAM for efficient data transmission systems, we believe our results could find application in communications protocols involving distant nodes.
(1), 013701, which focused on overall optical gain in open-loop configurations, our study examines how structured light modulates the spatial distribution of Raman gain. Using a density-matrix approach, we numerically obtain two-dimensional maps and cross-sectional profiles of Raman gain. The results show that three parameters-the orbital angular momentum (OAM) of the LG beam, the single-photon detuning, and the relative phase of the control fields-collectively determine the spatial morphology of the gain. OAM controls the transition between single-lobe and multi-lobe structures, modulates the gain magnitude and spatial complexity, and the relative phase induces rotational or mirror-symmetric transformations. This work provides the first systematic analysis of spatial Raman-gain modulation in a closed-loop three-level system, demonstrating the strong capability of structured light to tailor nonlinear gain processes. The findings extend the theoretical framework beyond PRA 2024 and offer insights for spatially selective amplification and structured-light-based photonic device design.
The paper reports on the storage of superposition of orbital angular momentum (OAM) states, as well as its manipulation through an applied transverse magnetic field. In the experiment , Zeeman sublevels of the degenerate two-level system is used. In another series of experiments,an external dc magnetic field is applied, nearly orthogonal to the plane defined by the incident beams. In this case,a series of collapses and revivals of the stored Zeeman coherence is observed. These observations demonstrate that superposition of OAM states can be stored into the atomic ensemble, and also the reversible transfer of OAM between light and atoms. Moreover, it also shows that the stored OAM can be manipulated with an external magnetic field.
Abstract The rich structure of transverse spatial modes of structured light has facilitated their extensive applications in quantum information and optical communication. The Laguerre–Gaussian (LG) modes, which carry a well-defined orbital angular momentum (OAM), consist of a complete orthogonal basis describing the transverse spatial modes of light. The application of OAM in free-space optical communication is restricted due to the experimentally limited OAM numbers and the complex OAM recognition methods. Here, we present a novel method that uses the advanced deep learning technique for LG modes recognition. By discretizing the spatial modes of structured light, we turn the OAM state regression into classification. A proof-of-principle experiment is also performed, showing that our method effectively categorizes OAM states with small training samples and the accuracy exceeds 99% from three-dimensional (3D) to fifteen-dimensional (15D) space. By assigning each category a classical information, we further apply our approach to an image transmission task, achieving a transmission accuracy of 99.58%, which demonstrates the ability to encode large data with low OAM number. This work opens up a new avenue for achieving high-capacity optical communication with low OAM number based on structured light.
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.