Laguerre-Gaussian Beams Research Articles

Beam Spreading Scaling Law of Focused Laguerre-Gaussian Beam Propagating through Oceanic Turbulence

Beam Spreading Scaling Law of Focused Laguerre-Gaussian Beam Propagating through Oceanic Turbulence

Giant Vortex Dichroism in Simplified-Chiral-Double-Elliptical Metamaterials

Vortex dichroism in chiral metamaterials is of great significance to the study of photoelectric detection, optical communication, and the interaction between light and matter. Here we propose a compact chiral metamaterials structure composed of two elliptical SiO2 rods covered with a Au film on a substrate to achieve a significant vortex-dichroism effect. Such a structure has different responses to a Laguerre-Gaussian beam carrying opposite-orbital angular momentum, resulting in giant vortex dichroism. The influences of various structural parameters are analyzed, and the optimal parameters are obtained to realize a remarkable vortex dichroism of about 58.5%. The simplicity and giant VD effect of the proposed metamaterials make it a promising candidate for advancing chiral optical applications such as optical communication and sensing.

Dynamics of dual-orbit rotations of nanoparticles induced by spin–orbit coupling

Abstract Spin–orbit coupling (SOC) in tightly focused optical fields offers a powerful mechanism for manipulating the complex motion of particles. However, to date, such a mechanism has only been applied to the single-orbit motion for particles, while multi-orbital dynamics have not yet been experimentally demonstrated. Here, the theoretical and experimental realization of dual-orbit rotational dynamics of nanoparticles in a tightly focused circularly polarized Laguerre-Gaussian beam is reported. Analyses reveal that the dual-orbit rotation of nanoparticles originates from SOC in a tightly focused vortex beam, with the motion velocity and direction determined by the topological charge of the beam. Experimentally, the dual-orbit rotation of polystyrene nanoparticles was observed for the first time using an inverted optical tweezer. In addition, the rotation velocity showed a clear linear dependence on the topological charge of the incident beam. This work reveals the pivotal role of SOC in enabling precise dual-orbit control at the nanoscale, paving the way for applications in optical sorting, grinding and delivery of microparticles.

Characterizing propagation and vortex-splitting dynamics of Bessel-Gaussian beams in short-range atmospheric conditions.

This study explores the propagation dynamics of Bessel-Gaussian (BG) beams, focusing on vortex-splitting behavior under short-range atmospheric conditions with varying disturbances. Using the split-step beam propagation method, the research reveals that greater atmospheric turbulence and longer transmission distances enhance both the average vortex splitting distance and its variance while reducing the average topological charge of the received OAM mode. Conversely, laminar conditions promote beam stability. Results highlight the high sensitivity of vortex splitting to beam parameters, with topological charge playing a significant role in phase singularity formation and vortex complexity. Additionally, beam width and shape are critical, as larger widths intensify splitting under atmospheric disturbance. Notably, BG beams exhibit greater stability and less vortex splitting than Laguerre-Gaussian beams, particularly in turbulent environments at short distances. These insights advance the understanding of vortex beam dynamics, with important implications for atmospheric remote sensing applications.

Generation of generalized perfect vortex beam based on dielectric spin-multiplexed metasurface

Abstract The perfect vortex beam (PVB) possesses an annular intensity profile diameter independent of topological charge, which has attracted much attention owing to the ability of improving optical fiber transmission efficiency. The composite perfect vortex beam (CPVB) is mainly based on the superposed multiple Laguerre-Gaussian beams with specific polarization states, which possesses topological charge-relevant spot shaped intensity pattern and the topological charge-irrelevant profile diameter. A series of spin-multiplexed metasurfaces have been designed to generate different PVB and CPVB under different spin light. The CPVB can also be modulated in scaling and rotating manner, which can broaden the dimensions of information. A spin-multiplexed metasurface has also been designed to generate CPVB array with different rotation angles and spot number under different spin light, and the encoding process has also been demonstrated. The uniqueness of these metasurfaces makes this design philosophy very attractive for applications in spin photonics, information encryption, optical communication, and optical information storage.

Magneto-optical polarization texturing

Left and right circularly polarized transverse electromagnetic waves propagate at slightly different speeds in a magnetic material leading to a polarization rotation by an amount proportional to the projection of the magnetic field along the direction of the wave propagation. We show how this magneto-optical effect can serve as a vectorial polarization shaper if the input mode is either a radially-polarized or an azimuthally-polarized Laguerre-Gaussian (LG) mode. The specific polarization map of the output field can be achieved by choosing appropriately the magnetic material and/or its geometry. We show further that when the LG beam waist is comparable to the wavelength (i.e. w 0 ≈ λ ) the fields are no longer purely transverse but acquire an additional longitudinal (axial) component. We demonstrate how this modifies the polarization texturing.

Design for light-based spherical aberration correction of ultrafast electron microscopes.

We theoretically demonstrate that ponderomotive interactions near the electron cross-over can be used for aberration correction in ultrafast electron microscopes. Highly magnified electron shadow images from Si3N4 thin films are utilized to visualize the distortions induced by spherical aberrations. Our simulations of electron-light interactions indicate that spherical aberrations can be compensated resulting in an aberration-free angle of 8.1 mrad. For achieving the necessary light distribution, we use a gradient descent algorithm to optimize Zernike polynomials and shape the light beam into a modified Gaussian and Laguerre-Gaussian beam.

Schmidt modes carrying orbital angular momentum generated by cascaded systems pumped with Laguerre–Gaussian beams

Schmidt modes carrying orbital angular momentum generated by cascaded systems pumped with Laguerre–Gaussian beams

Optical bottle beam transmit in polycyclic tornado mode

Light-field shaping technology is of significant importance for applications in particle trapping and optical communication. In this paper, we generate a new class of tunable polycyclic tornado Laguerre-Gaussian beams (TPTLGBs) experimentally and numerically by applying an annular spiral-zone phase (ASZP) with the second order chirped factor to Laguerre-Gaussian beams. By the parameters of the ASZP, we can modulate the focusing and diffraction of TPTLGBs along z-axis, controlling the number and quality of optical bottles (OBs) formed. In addition, it is possible to precisely control the direction of rotation of TPTLGBs during propagation. We further explore the specific effects of the ASZP and the central vortex phase on TPTLGBs. Adjusting the parameters of TPTLGBs, we obtain a high intensity focus. The multi-dimensional tunability and complex phase structure of TPTLGBs also provide new possibilities for further development of optical technology.

Transfer of optical orbital angular momentum under nonreciprocity-reciprocity amplification conversion

Magnet-free optical nonreciprocity has significant applications in quantum communication, quantum networks, and optical information processing. In this research, considering a degenerate two-level thermal atomic system with the Doppler effect of thermal atoms, the nonreciprocal amplification (NRA) of dual-path degenerate four-wave mixing (FWM) signals is achieved under the action of a co-propagating pumping field. On this basis, spatially multiplexed multiple FWM processes are formed by introducing another counter-propagating pumping field, thereby the reciprocal amplification (RA) of the dual-channel FWM signals is realized. Furthermore, by using multiple sets of spiral phase plates to load spiral phases on the signal light and the pumping light respectively, higher-order Laguerre-Gaussian vortex beams carrying different optical orbital angular momentum (OAM) are generated and participated in the FWM process, which achieve the transfer of the OAM of the pumping light to the amplified FWM fields. Simultaneously, using the Mach-Zehnder interferometer, the conservation characteristics of the OAM of each FWM signal in the NRA-RA conversion are further analyzed. Furthermore, experimental results have demonstrated that in the multiple FWM process induced by a pair of counter-propagating pump fields, the OAM of the amplified FWM signal in each channel varies with the change of that of the pump field. However, the overall process maintains the OAM conservation. The study provides a feasible solution for expanding channel capacity using OAM based on NRA-RA system, and has potential application prospects in achieving high-capacity optical communication and multi-channel signal processing.

Research on Orbital Angular Momentum Mode Detection in an Atmospheric Environment with Fusion Transfer Learning

The vortex beam carrying Orbital Angular Momentum (OAM) has infinite orthogonal characteristic states, which theoretically can infinitely increase the communication transmission capacity, thus attracting much attention in the field of optical communication. Due to the large amount of data required for training each OAM mode, the increase in channel capacity leads to an exponential growth in the required data volume. At the same time, the phase wavefront distortion caused by atmospheric turbulence (AT) further increases the difficulty of OAM pattern recognition. This article introduces transfer learning into the field of OAM modal detection and establishes an OAM modal classifier for detecting the topological charge of distorted vortex beams. The influence of different data volumes, turbulence intensities, and propagation distances on the accuracy of OAM modal detection during the transmission of Laguerre Gaussian beams in atmospheric turbulent channels is studied, and the generalization ability of the model is analyzed. The results show that compared with traditional convolutional neural networks, the modal classifier proposed in this paper reduces the dataset size to 1/10 of the original and successfully improves the OAM detection accuracy by 15.84%. It also exhibits good generalization under unknown atmospheric turbulence strengths, providing a new approach for identifying OAM modes.

Free-space propagation of double-ring perfect optical vortex beams

Abstract Single-ring perfect optical vortex (SR-POV) beams have received significant attention from the singular optics community due to their topological charge (TC)-independent ring radius, which offers certain advantages over conventional vortex beams such as Laguerre-Gaussian (LG) and Bessel-Gaussian (BG) beams in applications like particle trapping, optical communication, and imaging. However, the generation of double-ring perfect optical vortices (DR-POVs), embedded with two TCs, offers greater advantages over SR-POVs in terms of robustness during propagation and enhanced channel capacity in communication networks. In our theoretical analysis, we first highlight the differences between true and approximated representations of DR-POV beams. We then investigate the propagation of DR-POV beams in free-space, demonstrating how their evolution is influenced by factors such as the TCs of the inner and outer rings, the ratio of the beam radius to beam width at the waist plane. Similar to SR-POV beams, DR-POV beams exhibit non-diffracting behavior over short propagation distances, with little to no impact on the beam’s propagation when the TCs of the inner and outer rings are altered. However, phase wandering characteristics are observed, even over short propagation distances. Our research could find potential applications in the field of free-space optical communication.

Underwater Laguerre-Gaussian beam propagation and phase compensation method

Laguerre-Gaussian (LG) beams experience phase twist after long-distance transmission, making the orbital angular momentum (OAM) indistinguishable. This phenomenon becomes more severe in water due to the higher refractive index. Based on the physical principles of LG beams, this paper derives the mathematical expression for LG beam transmission in water to address this issue. It organizes and analyses the physical significance of each term. The exponential term responsible for phase twist is separated and phase compensation is applied to the initial LG beam. Simulation results show that after transmission through water, traditional LG beams exhibit a clockwise twisted distribution of isophase lines. By applying the phase compensation method proposed in this paper, the phase of the initial LG beam is modulated and when the LG beam reaches the observation plane, the isophase lines become straight, verifying the effectiveness of the method. This compensation method holds significant value for LG beams in advanced physics research.

Circularly coherent vortex beams with coherence singularities in free-space propagation

Circularly coherent sources, which are perfectly coherent on any ring that is concentric to the beam center, can preserve the spiral phase structures of optical vortices on propagation, making them potentially useful for free-space applications such as communications and remote sensing. In this study, we theoretically examine circularly coherent vortex beams by imposing circular coherence on Laguerre-Gaussian (LG) beams. The second-order coherence properties and coherence singularities of these circularly coherent vortex beams are investigated in free-space propagation up to 3 km. We discuss the noteworthy features of such beams, including self-focusing that arises due to the circular coherence.

Dihedral beams

Abstract In this work, a group theory-based formulation that introduces new classes of dihedral-symmetric beams is presented. Our framework leverages the algebraic properties of the dihedral group of rotations and reflections to transform input beams into closed-form families of dihedral-invariant wavefields, which will be referred to as dihedral beams. Each transformation is associated with a specific dihedral group in such a way that each family of dihedral beams exhibits the symmetries of its corresponding group. Our approach is inspired by one of the outcomes of this work: elegant Hermite–Gauss beams can be described as a dihedral interference pattern of elegant traveling waves, a new set of solutions to the paraxial equation also developed in this paper. Particularly, when taking elegant traveling waves as input beams, they transform into elegant dihedral beams possessing quasi-crystalline properties and including features like phase singularities, self-healing, and pseudo-nondiffracting propagation, as well as containing elegant Hermite and Laguerre–Gauss beams as special cases. Our approach can be applied to arbitrary scalar and vector input beams and constitutes a general group-theory formulation that can be extended beyond the dihedral group.

High-order harmonic generation driven by perfect optical vortex beams: Exploring the orbital angular momentum upscaling law

Orbital angular momentum (OAM) light beams for high-order harmonic generation (HHG) provide an additional degree of freedom to study the light-matter interaction at ultrafast timescales. A more sophisticated configuration is a perfect optical vortex (POV) beam, a light beam with a helical wave front characterized by a phase singularity at its center and an azimuthal phase variation. POV beams are characterized by a radial profile which is independent of the OAM. Here, we study the nonperturbative process of gas-phase HHG using a linearly polarized POV beam. We observe that the harmonics are emitted with similar divergence due to the perfectness of the POV-driven harmonic generation. Furthermore, the topological charge upscaling is rigorously followed. We show that a POV beam is more advantageous than that of the Laguerre-Gaussian beam for cases where a large topological charge with a small core size is required. Our research establishes a pathway for producing bright structured extreme ultraviolet coherent radiation sources—a pivotal tool with multifaceted applications across various technological domains. Published by the American Physical Society 2024

Spin Hall Effect of Laguerre-Gaussian and Bessel-Gaussian Beams Superimposed with Linearly Polarized Beams

Spin Hall Effect of Laguerre-Gaussian and Bessel-Gaussian Beams Superimposed with Linearly Polarized Beams

Astigmatic Laguerre–Gaussian Beams with Rapid Oscillations of Orbital Angular Momentum

Astigmatic Laguerre–Gaussian Beams with Rapid Oscillations of Orbital Angular Momentum

Formation and Control of the Polarization Structure of Vector Structured Laguerre-Gaussian Beams

Formation and Control of the Polarization Structure of Vector Structured Laguerre-Gaussian Beams

Study of the Influence of Turbulent Media on the Propagation of Squared Laguerre-Gaussian Beams

Study of the Influence of Turbulent Media on the Propagation of Squared Laguerre-Gaussian Beams