Physics and Astronomy Atomic and Molecular Physics, and Optics

Orbital Angular Momentum in Optics

Description

This cluster of papers covers a wide range of topics related to advances in optical manipulation, including orbital angular momentum, light beams, optical tweezers, structured light, plasmonic nano-optical tweezers, quantum communication, microfluidic sorting, singular optics, and spin-orbit interaction.

Keywords

Optical Manipulation; Orbital Angular Momentum; Light Beams; Optical Tweezers; Structured Light; Plasmonic Nano-optical Tweezers; Quantum Communication; Microfluidic Sorting; Singular Optics; Spin-Orbit Interaction

We present exact, nonsingular solutions of the scalar-wave equation for beams that are nondiffracting. This means that the intensity pattern in a transverse plane is unaltered by propagating in free … We present exact, nonsingular solutions of the scalar-wave equation for beams that are nondiffracting. This means that the intensity pattern in a transverse plane is unaltered by propagating in free space. These beams can have extremely narrow intensity profiles with effective widths as small as several wavelengths and yet possess an infinite depth of field. We further show (by using numerical simulations based on scalar diffraction theory) that physically realizable finite-aperture approximations to the exact solutions can also possess an extremely large depth of field.
We report the confinement and cooling of an optically dense cloud of neutral sodium atoms by radiation pressure. The trapping and damping forces were provided by three retroreflected laser beams … We report the confinement and cooling of an optically dense cloud of neutral sodium atoms by radiation pressure. The trapping and damping forces were provided by three retroreflected laser beams propagating along orthogonal axes, with a weak magnetic field used to distinguish between the beams. We have trapped as many as ${10}^{7}$ atoms for 2 min at densities exceeding ${10}^{11}$ atoms ${\mathrm{cm}}^{\ensuremath{-}3}$. The trap was \ensuremath{\simeq}0.4 K deep and the atoms, once trapped, were cooled to less than a millikelvin and compacted into a region less than 0.5 mm in diameter.
We propose an interferometric method for measuring the orbital angular momentum of single photons. We demonstrate its viability by sorting four different orbital angular momentum states, and are thus able … We propose an interferometric method for measuring the orbital angular momentum of single photons. We demonstrate its viability by sorting four different orbital angular momentum states, and are thus able to encode two bits of information on a single photon. This new approach has implications for entanglement experiments, quantum cryptography and high density information transfer.
Internet data traffic capacity is rapidly reaching limits imposed by optical fiber nonlinear effects. Having almost exhausted available degrees of freedom to orthogonally multiplex data, the possibility is now being … Internet data traffic capacity is rapidly reaching limits imposed by optical fiber nonlinear effects. Having almost exhausted available degrees of freedom to orthogonally multiplex data, the possibility is now being explored of using spatial modes of fibers to enhance data capacity. We demonstrate the viability of using the orbital angular momentum (OAM) of light to create orthogonal, spatially distinct streams of data-transmitting channels that are multiplexed in a single fiber. Over 1.1 kilometers of a specially designed optical fiber that minimizes mode coupling, we achieved 400-gigabits-per-second data transmission using four angular momentum modes at a single wavelength, and 1.6 terabits per second using two OAM modes over 10 wavelengths. These demonstrations suggest that OAM could provide an additional degree of freedom for data multiplexing in future fiber networks.
We present a method to efficiently sort orbital angular momentum (OAM) states of light using two static optical elements. The optical elements perform a Cartesian to log-polar coordinate transformation, converting … We present a method to efficiently sort orbital angular momentum (OAM) states of light using two static optical elements. The optical elements perform a Cartesian to log-polar coordinate transformation, converting the helically phased light beam corresponding to OAM states into a beam with a transverse phase gradient. A subsequent lens then focuses each input OAM state to a different lateral position. We demonstrate the concept experimentally by using two spatial light modulators to create the desired optical elements, applying it to the separation of eleven OAM states.
We experimentally demonstrate for the first time that a radially polarized field can be focused to a spot size significantly smaller [0.16(1)lambda(2)] than for linear polarization (0.26lambda(2)). The effect of … We experimentally demonstrate for the first time that a radially polarized field can be focused to a spot size significantly smaller [0.16(1)lambda(2)] than for linear polarization (0.26lambda(2)). The effect of the vector properties of light is shown by a comparison of the focal intensity distribution for radially and azimuthally polarized input fields. For strong focusing, a radially polarized field leads to a longitudinal electric field component at the focus which is sharp and centered at the optical axis. The relative contribution of this component is enhanced by using an annular aperture.
We report the first observation of Airy optical beams. This intriguing class of wave packets, initially predicted by Berry and Balazs in 1979, has been realized in both one- and … We report the first observation of Airy optical beams. This intriguing class of wave packets, initially predicted by Berry and Balazs in 1979, has been realized in both one- and two-dimensional configurations. As demonstrated in our experiments, these Airy beams can exhibit unusual features such as the ability to remain diffraction-free over long distances while they tend to freely accelerate during propagation.
It is shown that a low-density gas can be cooled by illuminating it with intense, quasi-monochromatic light confined to the lower-frequency half of a resonance line's Doppler width. Translational kinetic … It is shown that a low-density gas can be cooled by illuminating it with intense, quasi-monochromatic light confined to the lower-frequency half of a resonance line's Doppler width. Translational kinetic energy can be transferred from the gas to the scattered light, until the atomic velocity is reduced by the ratio of the Doppler width to the natural line width.
Cylindrical-vector beams are of increasing recent interest for their role in novel laser resonators and their applications to electron acceleration and scanning microscopy. In this paper, we calculate cylindrical-vector fields, … Cylindrical-vector beams are of increasing recent interest for their role in novel laser resonators and their applications to electron acceleration and scanning microscopy. In this paper, we calculate cylindrical-vector fields, near the focal region of an aplanatic lens, and briefly discuss some applications. We show that, in the particular case of a tightly focused, radially polarized beam, the polarization shows large inhomogeneities in the focal region, while the azimuthally polarized beam is purely transverse even at very high numerical apertures.
We use a Laguerre–Gaussian laser mode within an optical tweezers arrangement to demonstrate the transfer of the orbital angular momentum of a laser mode to a trapped particle. The particle … We use a Laguerre–Gaussian laser mode within an optical tweezers arrangement to demonstrate the transfer of the orbital angular momentum of a laser mode to a trapped particle. The particle is optically confined in three dimensions and can be made to rotate; thus the apparatus is an optical spanner. We show that the spin angular momentum of ±ℏ per photon associated with circularly polarized light can add to, or subtract from, the orbital angular momentum to give a total angular momentum. The observed cancellation of the spin and orbital angular momentum shows that, as predicted, a Laguerre–Gaussian mode with an azimuthal mode index l=1 has a well-defined orbital angular momentum corresponding to ℏ per photon.
Single molecules of double-stranded DNA (dsDNA) were stretched with force-measuring laser tweezers. Under a longitudinal stress of ∼65 piconewtons (pN), dsDNA molecules in aqueous buffer undergo a highly cooperative transition … Single molecules of double-stranded DNA (dsDNA) were stretched with force-measuring laser tweezers. Under a longitudinal stress of ∼65 piconewtons (pN), dsDNA molecules in aqueous buffer undergo a highly cooperative transition into a stable form with 5.8 angstroms rise per base pair, that is, 70% longer than B-form dsDNA. When the stress was relaxed below 65 pN, the molecules rapidly and reversibly contracted to their normal contour lengths. This transition was affected by changes in the ionic strength of the medium and the water activity or by cross-linking of the two strands of dsDNA. Individual molecules of single-stranded DNA were also stretched giving a persistence length of 7.5 angstroms and a stretch modulus of 800 pN. The overstretched form may play a significant role in the energetics of DNA recombination.
We explain that, unlike the spin angular momentum of a light beam which is always intrinsic, the orbital angular momentum may be either extrinsic or intrinsic. Numerical calculations of both … We explain that, unlike the spin angular momentum of a light beam which is always intrinsic, the orbital angular momentum may be either extrinsic or intrinsic. Numerical calculations of both spin and orbital angular momentum are confirmed by means of experiments with particles trapped off axis in optical tweezers, where the size of the particle means it interacts with only a fraction of the beam profile. Orbital angular momentum is intrinsic only when the interaction with matter is about an axis where there is no net transverse momentum.
Laser light with a Laguerre-Gaussian amplitude distribution is found to have a well-defined orbital angular momentum. An astigmatic optical system may be used to transform a high-order Laguerre-Gaussian mode into … Laser light with a Laguerre-Gaussian amplitude distribution is found to have a well-defined orbital angular momentum. An astigmatic optical system may be used to transform a high-order Laguerre-Gaussian mode into a high-order Hermite-Gaussian mode reversibly. An experiment is proposed to measure the mechanical torque induced by the transfer of orbital angular momentum associated with such a transformation.
We show numerically that vector antenna arrays can generate radio beams that exhibit spin and orbital angular momentum characteristics similar to those of helical Laguerre-Gauss laser beams in paraxial optics. … We show numerically that vector antenna arrays can generate radio beams that exhibit spin and orbital angular momentum characteristics similar to those of helical Laguerre-Gauss laser beams in paraxial optics. For low frequencies ($\ensuremath{\lesssim}1\text{ }\text{ }\mathrm{GHz}$), digital techniques can be used to coherently measure the instantaneous, local field vectors and to manipulate them in software. This enables new types of experiments that go beyond what is possible in optics. It allows information-rich radio astronomy and paves the way for novel wireless communication concepts.
The techniques of optical trapping and manipulation of neutral particles by lasers provide unique means to control the dynamics of small particles. These new experimental methods have played a revolutionary … The techniques of optical trapping and manipulation of neutral particles by lasers provide unique means to control the dynamics of small particles. These new experimental methods have played a revolutionary role in areas of the physical and biological sciences. This paper reviews the early developments in the field leading to the demonstration of cooling and trapping of neutral atoms in atomic physics and to the first use of optical tweezers traps in biology. Some further major achievements of these rapidly developing methods also are considered.
D ESIGN CON SID ERATION S . . . . . . . . . . . . . . . . . . . . . . . . … D ESIGN CON SID ERATION S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 Bll/ding a Trap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 Beam Steering 254 Trapping Lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 T RAPPIN G TH EORY . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . .. . . . . . . . . . . . ... . . . . 260 Ray-Optics Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262 Electromagnetic Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264 F ORCE M EASUREM EN T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267 Measurement of Trap Stiffness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270 Physics of Trup Stiffness Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 B�ownia,! Motion During Force Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . 272 PlcotenslOmeters 273 Other Applications of Picotensiometry .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 Determinants of Trapping Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277
We demonstrate experimentally an optical process in which the spin angular momentum carried by a circularly polarized light beam is converted into orbital angular momentum, leading to the generation of … We demonstrate experimentally an optical process in which the spin angular momentum carried by a circularly polarized light beam is converted into orbital angular momentum, leading to the generation of helical modes with a wave-front helicity controlled by the input polarization. This phenomenon requires the interaction of light with matter that is both optically inhomogeneous and anisotropic. The underlying physics is also associated with the so-called Pancharatnam-Berry geometrical phases involved in any inhomogeneous transformation of the optical polarization.
Optical trapping of dielectric particles by a single-beam gradient force trap was demonstrated for the first reported time. This confirms the concept of negative light pressure due to the gradient … Optical trapping of dielectric particles by a single-beam gradient force trap was demonstrated for the first reported time. This confirms the concept of negative light pressure due to the gradient force. Trapping was observed over the entire range of particle size from 10 μm to ~25 nm in water. Use of the new trap extends the size range of macroscopic particles accessible to optical trapping and manipulation well into the Rayleigh size regime. Application of this trapping principle to atom trapping is considered.
We demonstrate controlled rotation of optically trapped objects in a spiral interference pattern. This pattern is generated by interfering an annular shaped laser beam with a reference beam. Objects are … We demonstrate controlled rotation of optically trapped objects in a spiral interference pattern. This pattern is generated by interfering an annular shaped laser beam with a reference beam. Objects are trapped in the spiral arms of the pattern. Changing the optical path length causes this pattern, and thus the trapped objects, to rotate. Structures of silica microspheres, microscopic glass rods, and chromosomes are set into rotation at rates in excess of 5 hertz. This technique does not depend on intrinsic properties of the trapped particle and thus offers important applications in optical and biological micromachines.
As they travel through space, some light beams rotate. Such light beams have angular momentum. There are two particularly important ways in which a light beam can rotate: if every … As they travel through space, some light beams rotate. Such light beams have angular momentum. There are two particularly important ways in which a light beam can rotate: if every polarization vector rotates, the light has spin; if the phase structure rotates, the light has orbital angular momentum (OAM), which can be many times greater than the spin. Only in the past 20 years has it been realized that beams carrying OAM, which have an optical vortex along the axis, can be easily made in the laboratory. These light beams are able to spin microscopic objects, give rise to rotational frequency shifts, create new forms of imaging systems, and behave within nonlinear material to give new insights into quantum optics.
Conventional optical components rely on gradual phase shifts accumulated during light propagation to shape light beams. New degrees of freedom are attained by introducing abrupt phase changes over the scale … Conventional optical components rely on gradual phase shifts accumulated during light propagation to shape light beams. New degrees of freedom are attained by introducing abrupt phase changes over the scale of the wavelength. A two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint such phase discontinuities on propagating light as it traverses the interface between two media. Anomalous reflection and refraction phenomena are observed in this regime in optically thin arrays of metallic antennas on silicon with a linear phase variation along the interface, which are in excellent agreement with generalized laws derived from Fermat's principle. Phase discontinuities provide great flexibility in the design of light beams, as illustrated by the generation of optical vortices through use of planar designer metallic interfaces.
One property of electromagnetic waves that has been recently explored is the ability to multiplex multiple beams, such that each beam has a unique helical phase front. The amount of … One property of electromagnetic waves that has been recently explored is the ability to multiplex multiple beams, such that each beam has a unique helical phase front. The amount of phase front ‘twisting’ indicates the orbital angular momentum state number, and beams with different orbital angular momentum are orthogonal. Such orbital angular momentum based multiplexing can potentially increase the system capacity and spectral efficiency of millimetre-wave wireless communication links with a single aperture pair by transmitting multiple coaxial data streams. Here we demonstrate a 32-Gbit s−1 millimetre-wave link over 2.5 metres with a spectral efficiency of ~16 bit s−1 Hz−1 using four independent orbital–angular momentum beams on each of two polarizations. All eight orbital angular momentum channels are recovered with bit-error rates below 3.8 × 10−3. In addition, we demonstrate a millimetre-wave orbital angular momentum mode demultiplexer to demultiplex four orbital angular momentum channels with crosstalk less than −12.5 dB and show an 8-Gbit s−1 link containing two orbital angular momentum beams on each of two polarizations. High speed data transmission using orbital angular momentum beams has been recently demonstrated. Here, Yan et al. demonstrate a 32 Gbit/s millimetre-wave communication link using eight coaxially propagating independent orbital angular momentum beams with four orbital angular momentum states on two orthogonal polarizations.
We investigate the acceleration dynamics of quasi-diffraction-free Airy beams in both one- and two-dimensional configurations. We show that this class of finite energy waves can retain their intensity features over … We investigate the acceleration dynamics of quasi-diffraction-free Airy beams in both one- and two-dimensional configurations. We show that this class of finite energy waves can retain their intensity features over several diffraction lengths. The possibility of other physical realizations involving spatiotemporal Airy wave packets is also considered.
We demonstrate the transfer of information encoded as orbital angular momentum (OAM) states of a light beam. The transmitter and receiver units are based on spatial light modulators, which prepare … We demonstrate the transfer of information encoded as orbital angular momentum (OAM) states of a light beam. The transmitter and receiver units are based on spatial light modulators, which prepare or measure a laser beam in one of eight pure OAM states. We show that the information encoded in this way is resistant to eavesdropping in the sense that any attempt to sample the beam away from its axis will be subject to an angular restriction and a lateral offset, both of which result in inherent uncertainty in the measurement. This gives an experimental insight into the effects of aperturing and misalignment of the beam on the OAM measurement and demonstrates the uncertainty relationship for OAM.
An overview of the recent developments in the field of cylindrical vector beams is provided. As one class of spatially variant polarization, cylindrical vector beams are the axially symmetric beam … An overview of the recent developments in the field of cylindrical vector beams is provided. As one class of spatially variant polarization, cylindrical vector beams are the axially symmetric beam solution to the full vector electromagnetic wave equation. These beams can be generated via different active and passive methods. Techniques for manipulating these beams while maintaining the polarization symmetry have also been developed. Their special polarization symmetry gives rise to unique high-numerical-aperture focusing properties that find important applications in nanoscale optical imaging and manipulation. The prospects for cylindrical vector beams and their applications in other fields are also briefly discussed.
Orbital angular momentum (OAM), which describes the "phase twist" (helical phase pattern) of light beams, has recently gained interest due to its potential applications in many diverse areas. Particularly promising … Orbital angular momentum (OAM), which describes the "phase twist" (helical phase pattern) of light beams, has recently gained interest due to its potential applications in many diverse areas. Particularly promising is the use of OAM for optical communications since: (i) coaxially propagating OAM beams with different azimuthal OAM states are mutually orthogonal, (ii) inter-beam crosstalk can be minimized, and (iii) the beams can be efficiently multiplexed and demultiplexed. As a result, multiple OAM states could be used as different carriers for multiplexing and transmitting multiple data streams, thereby potentially increasing the system capacity. In this paper, we review recent progress in OAM beam generation/detection, multiplexing/demultiplexing, and its potential applications in different scenarios including free-space optical communications, fiber-optic communications, and RF communications. Technical challenges and perspectives of OAM beams are also discussed.
Optical elements that convert the spin angular momentum (SAM) of light into vortex beams have found applications in classical and quantum optics. These elements-SAM-to-orbital angular momentum (OAM) converters-are based on … Optical elements that convert the spin angular momentum (SAM) of light into vortex beams have found applications in classical and quantum optics. These elements-SAM-to-orbital angular momentum (OAM) converters-are based on the geometric phase and only permit the conversion of left- and right-circular polarizations (spin states) into states with opposite OAM. We present a method for converting arbitrary SAM states into total angular momentum states characterized by a superposition of independent OAM. We designed a metasurface that converts left- and right-circular polarizations into states with independent values of OAM and designed another device that performs this operation for elliptically polarized states. These results illustrate a general material-mediated connection between SAM and OAM of light and may find applications in producing complex structured light and in optical communication.
Abstract Thirty years ago, Coullet et al. proposed that a special optical field exists in laser cavities bearing some analogy with the superfluid vortex. Since then, optical vortices have been … Abstract Thirty years ago, Coullet et al. proposed that a special optical field exists in laser cavities bearing some analogy with the superfluid vortex. Since then, optical vortices have been widely studied, inspired by the hydrodynamics sharing similar mathematics. Akin to a fluid vortex with a central flow singularity, an optical vortex beam has a phase singularity with a certain topological charge, giving rise to a hollow intensity distribution. Such a beam with helical phase fronts and orbital angular momentum reveals a subtle connection between macroscopic physical optics and microscopic quantum optics. These amazing properties provide a new understanding of a wide range of optical and physical phenomena, including twisting photons, spin–orbital interactions, Bose–Einstein condensates, etc., while the associated technologies for manipulating optical vortices have become increasingly tunable and flexible. Hitherto, owing to these salient properties and optical manipulation technologies, tunable vortex beams have engendered tremendous advanced applications such as optical tweezers, high-order quantum entanglement, and nonlinear optics. This article reviews the recent progress in tunable vortex technologies along with their advanced applications.
Since their invention just over 20 years ago, optical traps have emerged as a powerful tool with broad-reaching applications in biology and physics. Capabilities have evolved from simple manipulation to … Since their invention just over 20 years ago, optical traps have emerged as a powerful tool with broad-reaching applications in biology and physics. Capabilities have evolved from simple manipulation to the application of calibrated forces on-and the measurement of nanometer-level displacements of-optically trapped objects. We review progress in the development of optical trapping apparatus, including instrument design considerations, position detection schemes and calibration techniques, with an emphasis on recent advances. We conclude with a brief summary of innovative optical trapping configurations and applications.
Abstract Reconstructing 3D light fields from holograms mainly relies on iterative algorithms and deep learning. However, these strategies are often limited by time‐consuming and complex operations. Radially self‐accelerating beams exhibit … Abstract Reconstructing 3D light fields from holograms mainly relies on iterative algorithms and deep learning. However, these strategies are often limited by time‐consuming and complex operations. Radially self‐accelerating beams exhibit distinct rotational characteristics during propagation, making them well‐suited for various optical systems. This paper presents an innovative approach that combines the radially self‐accelerating beams with orbital angular momentum (OAM) holography and 3D point cloud technology to enable fast and accurate 3D light‐field reconstruction from a single‐shot image. In experiments, the beams are independently convolved onto the point cloud, allowing each point to rotate around the optical axis during propagation. A light neural network is designed to deduce the relative heights of all points based on rotation properties and to reconstruct the 3D light field in 0.7 s with an accuracy of over 93%. It is anticipated that this work will provide new opportunities in the fields of 3D object measurement, real‐time particle tracking, and the innovative application of OAM holographic multiplexing.
Abstract The spatiotemporal optical vortices (STOVs) carrying orbital angular momentum (OAM) perpendicular to the propagation direction have attracted increasing interest because they provide an additional optical degree of freedom. However, … Abstract The spatiotemporal optical vortices (STOVs) carrying orbital angular momentum (OAM) perpendicular to the propagation direction have attracted increasing interest because they provide an additional optical degree of freedom. However, a few critical problems hinder STOVs in possible applications. These problems include that the radius of STOVs is not constant and keeps growing with an increasing topological charge; high‐order STOVs have many sidelobes; the pulse shape is far from being a perfect circle because the pulse dimensions differ noticeably in the transverse and longitudinal directions. In this work, all these problems are overcome by theoretically and experimentally demonstrate the perfect STOVs with invariant radius and no sidelobes. The 3D reconstruction reveals a perfect single‐ring shape in the spatiotemporal plane, and the spectral interferometry unveils a spatiotemporal spiral phase of topological charge up to 18. This work paves the way for future applications of STOVs in classical and quantum data encryption and transmission, particle manipulation and OAM‐based sensing and measurement.
Abstract Dynamic switching between edge detection and bright‐field imaging modes is advantageous in optical imaging, particularly for biomedical diagnostics and material characterization. However, conventional approaches necessitate complex setups or intricate … Abstract Dynamic switching between edge detection and bright‐field imaging modes is advantageous in optical imaging, particularly for biomedical diagnostics and material characterization. However, conventional approaches necessitate complex setups or intricate fabrication processes, limiting their practicality. This study demonstrates a humidity‐responsive optical imaging system, enabling reversible and tunable transitions between edge‐enhanced and Gaussian‐like bright‐field imaging modes by leveraging humidity‐induced variations in the spin Hall effect of light. Utilizing polyvinyl alcohol films that exhibit reversible humidity‐dependent changes in thickness and refractive index, the Fresnel reflection coefficients ( and ) are effectively modulated, leading to asymmetric spin‐dependent beam splitting in both x‐ and y‐directions. These humidity‐driven variations disrupt the initial symmetric vortex conditions, namely that the in‐plane and out‐of‐plane shifts induced by the spin Hall effect of light are equal, transforming the topological vortex beam into a quasi‐Gaussian distribution. Consequently, the imaging performance shifts from edge‐enhanced mode to quasibright‐field mode as the relative humidity increases. Experimental validation using customized resolution targets and biological tissue samples (planaria and small intestine) demonstrates reliable and reproducible imaging mode switching without requiring mechanical adjustments or complex fabrication. Thus, the proposed system offers improved simplicity, operational convenience, and cost‐effectiveness compared to existing methods (e.g., metasurface‐based techniques), underscoring the potential of humidity‐tunable spin Hall effect of light‐based polymer optics for practical and versatile imaging applications.
ABSTRACT A 32 GHz radio‐over‐fiber (RoF) system using integrated mode division multiplexing (MDM) and optical code division multiple access (OCDMA) scheme is realized. Quad orbital angular momentum (OAM) based zero … ABSTRACT A 32 GHz radio‐over‐fiber (RoF) system using integrated mode division multiplexing (MDM) and optical code division multiple access (OCDMA) scheme is realized. Quad orbital angular momentum (OAM) based zero cross‐correlation OCDMA coded signals with time division multiplexing are transmitted over hybrid fiber‐free space optics (FSO) link under the impact of clear air, haze, light, and moderate fog conditions. Simulation results depict that the system offers a maximum 0.1 km fiber and 500 m FSO range at aggregate 30 Gbps throughput. Also, the system offers acceptable bit error rate performance with a maximum 14 μm spot size, 14 cm transmitter/receiver aperture diameters, and a minimum received power of −2 dBm. Compared to existing designs, this work offers optimum system performance.
Abstract Run-and-tumble particle (RTP) motion is a key model for certain bacteria
and other actively moving microscopic particles, combining phases of
directed motion with "tumbles", stationary phases during which the particle
reorients itself. … Abstract Run-and-tumble particle (RTP) motion is a key model for certain bacteria
and other actively moving microscopic particles, combining phases of
directed motion with "tumbles", stationary phases during which the particle
reorients itself. We here continue previous studies of
unconstrained RTP motion and consider the transition path properties of an
RTP subjected to an external potential. Exact expressions are derived
for the RTP transition path properties, supported by results from Monte
Carlo simulations. We explore the effects of particle velocity, tumble
rate and the external potential on the splitting probability, transition
path time, coefficient of variation, transition path shape, unsuccessful
transition path distribution and duration, based on forward and backward
master equations. Counterintuitively, the presence of the potential may
accelerate the escape of RTPs. Moreover, we show that the external potential
gives rise to the appearance of an asymmetry of the transition path properties
which increases with the steepness of the potential. While the potential
does not affect the forward and reverse transition paths of the RTP, these
are affected by the particle velocity, in contrast with free RTPs.
This study experimentally demonstrates transverse symmetry breaking—a mechanism governing laser planar trapping—and distinguishes its unique role from related phenomena such as the lateral Goos–Hänchen shift and angular deviations. While the … This study experimentally demonstrates transverse symmetry breaking—a mechanism governing laser planar trapping—and distinguishes its unique role from related phenomena such as the lateral Goos–Hänchen shift and angular deviations. While the latter effects describe positional or angular beam displacements at interfaces, transverse symmetry breaking fundamentally alters the beam’s spatial symmetry, enabling unprecedented control over its intensity and phase profiles. Empirical results exhibit exceptional agreement with a recently proposed theoretical model, validating its predictive capability. Crucially, our findings highlight transverse symmetry breaking as a critical tool for tailoring beam profiles, advancing applications in optical trapping, structured light systems, and photonic device engineering, where symmetry manipulation unlocks new degrees of freedom in light–matter interactions.
Abstract Coherent laser array (CLA) system is a promising solution for the engineering of multiple beams forming on demand, thereby facilitating long‐distance and multicasting free‐space optical communication links. However, it … Abstract Coherent laser array (CLA) system is a promising solution for the engineering of multiple beams forming on demand, thereby facilitating long‐distance and multicasting free‐space optical communication links. However, it is challenging to meet the demand of large‐volume transmission capacity in the current CLA architecture. This research transcends such a barrier by pioneering an intelligent large‐scale CLA system for realizing parallel orbital angular momentum (OAM) modes recognition via the convolutional neural network (CNN), thus enabling the development of high‐dimensional shift‐keying communication links. It is demonstrated to exhibit, within the established high‐dimensional communication links, that a total of 256 OAM modes can be classified accurately by resorting to the ResNet‐18, which achieves an ultra‐high precision of 99.69% and an infinitesimal bit error rate (BER) of 3.89 × 10 −4 . More impressively, the high‐dimensional optical links are nearly immune to practical phase errors and free of side‐lobe disturbances. In principle, compared with the traditional CLA system, more OAM modes can be recognized with the proposed system while maintaining superior communication performances. These achievements illustrate that the intelligent algorithm shows great potential in the construction of robust and high‐dimensional CLA‐based OAM shift‐keying optical links.
Abstract We implement a paraxial azimuthally-radially polarized beam (ARPB), a novel class of structured light beams that can be optimal chiral (OC), leading to maximum chirality density at a given … Abstract We implement a paraxial azimuthally-radially polarized beam (ARPB), a novel class of structured light beams that can be optimal chiral (OC), leading to maximum chirality density at a given energy density. By using vectorial light shaping techniques, we successfully generated a paraxial ARPB with precise control over its features, validating theoretical predictions. Our findings demonstrate the ability to finely adjust the chirality density of the ARPB across its entire range by manipulating a single beam parameter. Although our experimental investigations are primarily focused on the transverse plane, we show that fields whose transverse components satisfy the optimal chirality condition are optimally chiral in all directions, and our results highlight the promising potential of OC structured light for applications in the sensing and manipulation of chiral particles. We show that helicity density is more general than the concept of handedness. This work represents a significant advancement toward practical optical enantioseparation and enantiomer detection at the nanoscale.
Structured light is increasingly recognized by researchers as a tool for enhancing the degrees of control freedom and adaptability of optical tweezers. However, the challenge of employing a single beam … Structured light is increasingly recognized by researchers as a tool for enhancing the degrees of control freedom and adaptability of optical tweezers. However, the challenge of employing a single beam to navigate different planes and execute varied complex manipulations persists as a pressing concern. Herein, we present a solution by integrating coordinate transformation techniques with Airy vortex beams to generate orientation-selective Airy vortex beams. By preserving the inherent self-healing attributes of Airy beams, this approach enables the creation of arbitrary super-ellipse shapes (e.g., ellipse, square-like, and rectangular-like), each observed within distinct planes. Due to the non-circular symmetry of these shapes, their intensity distribution varies across different planes during propagation in 3D space. We experimentally demonstrate that orientation-selective Airy vortex beams operate on circular, elliptical, square-like, and rectangular-like trajectories at different 2D planes along the optical axis. These results enhance the trajectory of particles manipulated by spatially structured light fields in optical tweezers.
Abstract Direct intracavity generation of vortex beams with pulse durations below 100 fs based on Yb:CALGO vortex laser oscillator is proposed and investigated experimentally. The oscillator integrated semiconductor saturable absorber … Abstract Direct intracavity generation of vortex beams with pulse durations below 100 fs based on Yb:CALGO vortex laser oscillator is proposed and investigated experimentally. The oscillator integrated semiconductor saturable absorber mirror (SESAM)‐assisted Kerr mode‐locking with spot‐defect mirror technology. The SESAM‐assisted Kerr mode‐locking mechanism enabled phase locking between different longitudinal modes to obtain short pulses. Meanwhile, the spot‐defect mirror regulated transverse mode characteristics, optimizing the intracavity optical field distribution under longitudinal mode phase‐locking conditions. This synergistic approach enhanced nonlinear spatiotemporal mode coupling. By precisely adjusting the position of the spot‐defect mirror, a well‐defined Laguerre‐Gaussian (LG) mode profile is obtained when the defect is aligned with the cavity axis. Under these conditions, the Yb:CALGO vortex laser oscillator achieved a pulse duration as short as 75.7 fs, a spectral bandwidth of up to 18.2 nm, and a maximum output power of 3.2 W. To the best of the knowledge, this represents the shortest pulse duration for an ultrafast vortex beam generated directly from an oscillator.