Orbital Angular Momentum Of Light Research Articles

Harnessing spin and orbital angular momentum light for optimal algae growth

The present study investigated the difference in transmittance of light carrying opposite spin angular momentum (SAM) and orbital angular momentum (OAM) through chlorella algal fluid with varying concentrations and thicknesses. Our results indicate that, under specific conditions, right-handed light sources exhibit higher transmittance in the algal fluid compared to left-handed light sources. Furthermore, we observed that light with OAM also demonstrated higher transmittance than other types of light sources, leading to faster cell density growth of Chlorella. Interestingly, we also discovered that light with OAM stimulates Chlorella to synthesize more proteins. These findings provide different insights for selecting appropriate light sources for large-scale algae cultivation, and may facilitate the realization of carbon peaking and carbon neutrality in the future.

Effective gyration of polar vortex arrays controlled by high orbital angular momentum of light

Effective gyration of polar vortex arrays controlled by high orbital angular momentum of light

All-dielectric geometric metasurfaces for the generation and manipulation of perfect high-order Poincaré sphere beams

A high-order Poincaré sphere (HOPS) can be used to describe high-order modes of waveguides and vector beams, since it generalizes the feature of spin and the orbital angular momentum of light. HOPS beams are such beams with polarization states on the HOPS, which have potential applications in optical manipulation and optical communication. In general, the intensity distribution of this kind of beam changes with the topological charge, which limits their practical applications. Based on the concept of perfect vortex beams (PVBs), perfect HOPS beams have been proposed to solve this problem. Here, a flexible and compact scheme based on all-dielectric metasurfaces for realizing and manipulating perfect HOPS beams at near-infrared wavelength was demonstrated. Geometric-phase-only manipulation was employed for simultaneously controlling the phase and polarization of the incident light. By varying the incident polarization, several selected polarization states on the HOPS could be realized by the proposed metasurface. Further, the single ultra-thin metasurface can also realize high quality multiplexing perfect HOPS beams that carry different topological charges. Finally, a cascaded metasurface system has been proposed for generating and manipulating multiple HOPS beams. This compact flat-optics-based scheme for perfect HOPS beam generation and manipulation demonstrated here can be used for on-chip optical manipulation and integrated optical communication in the future.

Geometric interpretation and experimental test of Leggett inequalities with nonmaximally entangled states.

Leggett inequality states that nonlocal hidden-variable models might still be incompatible with the predictions of quantum physics. However, its theoretical and experimental demonstration is only in the scenario of 2-dimensional maximally entangled systems. An open question remains as to whether the Leggett inequality can be violated by nonmaximally entangled states. Here, we answer this question both in theory and experiment. Specifically, from the point of view of geometry, we theoretically map the problem of maximizing the correlation measure in the Leggett inequality to maximizing the sum of an ellipse's diameter and semi-diameter axes, accordingly, demonstrating that the violation of the Leggett inequality requires a more robust entanglement than that of Bell's theory. Experimentally, by leveraging the controllable photonic orbital angular momentum entanglement, we demonstrate the violation of Leggett-type inequalities by more than 8.7 and 4.5 standard deviations under concurrence C = 0.95 and 0.9, respectively. Our observations indicate that, the requirement for quantum correlation should be increased to exclude a particular class of non-local hidden variable theories that abide by Leggett's model, providing insights into the boundaries of quantum correlation and the limitations imposed by non-local hidden variables.

Spatiotemporal Torquing of Light

We demonstrate the controlled spatiotemporal transfer of transverse orbital angular momentum (OAM) to electromagnetic waves: the spatiotemporal torquing of light. This is a radically different situation from OAM transfer to longitudinal, spatially defined OAM light by stationary or slowly varying refractive-index structures such as phase plates or air turbulence. We show that net transverse OAM per photon can be spatiotemporally imparted to a light pulse only if (1) a transient phase perturbation is well overlapped with the pulse in spacetime, or (2) the pulse initially has nonzero transverse OAM density, and the perturbation removes energy from it. Physical insight is provided by the mechanical analogy of torquing a wheel or removing mass as it spins. Our OAM theory for spatiotemporal optical vortex (STOV) pulses [S. W. Hancock ,] correctly quantifies the light-matter interaction of our experiments and provides a spatiotemporal-torque-based explanation for the first measurement of STOVs [N. Jhajj , ]. Published by the American Physical Society 2024

Mapping of atoms via the coherence superpositions of orbital angular momentum light

We propose a scheme to map atoms via the coherence superpositions of orbital angular momentum (OAM) light. The atoms are prepared in the four-level tripod configuration in the presence of a vortex light, which coherently superposes two Laguerre-Gaussian (LG) beam modes with equal but opposite OAM. Because of the spatially dependent atom-field interaction, the information about the position of the atom can be obtained via the absorption measurement of the weak probe field. It is found that the absorption behavior is significantly impacted by the detuning, control field, azimuthal number, and radial number. Most importantly, atomic mapping accuracy can be controlled by properly adjusting the detunings and control field. The coherent interaction of OAM light with atoms constitutes a platform for active mapping of atoms at specific positions in azimuthal space.

Investigation of the OAM EM wave tissue irradiation at millimeter-wave frequencies

Recently, there has been an increase of interest in the use of electromagnetic (EM) waves with helical wavefronts, known as the orbital angular momentum (OAM) waves. Applications in the field of biomedicine have been foreseen, such as medical imaging and diagnosis, deep-tissue imaging, biosensing, and communication with medical implants. Other possible applications include various localized tissue treatments or tissue ablation. The available references mainly study the interaction of OAM light with biological structures, offering some insights into the biophotonics effects, but without the investigation of how to plan tissue exposures or how to estimate the EM field parameters in a particular case of application. We use the previously developed short dipole modeling of OAM EM fields to study the above problems by altering the OAM beam parameters and the distance from the target tissue. The results could guide the design of components and devices based on OAM EM waves.

Binary image encryption with a QR code-encoded optical beam having an array of vortices.

In recent years, optical information processing has become increasingly important due to its ability to handle large amounts of data efficiently. Amplitude, phase, spatial frequency, wavelength, and polarization are the physical dimensions used for information encoding into the light beam. Information encoding using orbital angular momentum (OAM) carried by a vortex beam is gaining interest in this regard. Such beams provide high-dimensional orthogonal states for encoding and have shown more stability in turbulent media than Gaussian beams, especially in the case of free space propagation. This study demonstrates an image encryption method utilizing an array of OAM light modes. The approach uses a non-interferometric intensity recording-based encoding scheme, which offers ease of implementation. Quick response codes have been utilized for encoding to avoid information loss from non-uniform distribution of light and aberrations. The encryption scheme is highly secure because the encrypted light beam contains only partial information about the object, preventing complete information retrieval without proper key information.

Intracavity spatially modulated metasurfaces for a wavelength-tunable figure-9 vortex fiber laser.

Intracavity optical metasurfaces with compact and flexible light manipulation capabilities, effectively enrich the implementation of miniaturized and user-friendly orbital angular momentum (OAM) laser sources. Here we demonstrate a wavelength-tunable figure-9 Yb-doped vortex fiber laser solely with standard non-polarization-maintaining single-mode fibers, which utilizes a gap-surface plasmon (GSP) metasurface as the intracavity mode regulation component to generate OAM beams, extending the avenues and related applications for cost-effective OAM laser sources. Gained by the broadband operation range of the metasurface, the figure-9 fiber laser could emit OAM light with center wavelength tunable from 1020 nm to 1060 nm and of high mode purity (about 90%). OAM beams with different topological charges such as l = ±1 have been obtained by changing the metasurface design. The proposed fiber laser with the intracavity GSP metasurface provides a reliable and customized output of OAM beams at the laser source, holding great promise for a wide range of applications in optical communications, sensing, and super-resolution imaging.

Fundamental probing limit on the high-order orbital angular momentum of light.

The orbital angular momentum (OAM) of light, possessing an infinite-dimensional degree of freedom, holds significant potential to enhance the capacity of optical communication and information processing in both classical and quantum regimes. Despite various methods developed to accurately measure OAM modes, the probing limit of the highest-order OAM remains an open question. Here, we report an accurate recognition of superhigh-order OAM using a convolutional neural network approach with an improved ResNeXt architecture, based on conjugated interference patterns. A type of hybrid beam carrying double OAM modes is utilized to provide more controllable degrees of freedom for greater recognition of the OAM modes. Our contribution advances the OAM recognition limit from manual counting to machine learning. Results demonstrate that, within our optical system, the maximum recognizable OAM modes exceed l = ±690 with an accuracy surpassing 99.93%, the highest achieved by spatial light modulator to date. Enlarging the active area of the CCD sensor extends the number of recognizable OAM modes to 1300, constrained only by the CCD resolution limit. Additionally, we explore the identification of fractional high-order OAM modes with a resolution of 0.1 from l = ±600.0 to l = ±600.9, achieving a high accuracy of 97.86%.

Nonlinear Boost of Optical Angular Momentum Selectivity by Hybrid Nanolaser Circuits.

Selective control of light is essential for optical science and technology, with numerous applications. However, optical selectivity in the angular momentum of light has been quite limited, remaining constant by increasing the incident light power on previous passive optical devices. Here, we demonstrate a nonlinear boost of optical selectivity in both the spin and orbital angular momentum of light through near-field selective excitation of single-mode nanolasers. Our designed hybrid nanolaser circuits consist of plasmonic metasurfaces and individually placed perovskite nanowires, enabling subwavelength focusing of angular-momentum-distinctive plasmonic fields and further selective excitation of nanolasers in nanowires. The optically selected nanolaser with a nonlinear increase of light emission greatly enhances the baseline optical selectivity offered by the metasurface from about 0.4 up to near unity. Our demonstrated hybrid nanophotonic platform may find important applications in all-optical logic gates and nanowire networks, ultrafast optical switches, nanophotonic detectors, and on-chip optical and quantum information processing.

Three-dimensional spatial orbital angular momentum holography

The degree of freedom of orbital angular momentum of light has been used as a new information carrier in optical holographic information processing technology. However, current research on orbital angular momentum holography mainly focuses on two-dimensional orbital angular momentum holography, where the reconstructed two-dimensional holographic image is located in a certain plane in three-dimensional space. How to further implement three-dimensional spatial orbital angular momentum holographic technology and use it to increase the information capacity of holographic communication is still a blank. Here, we implement three-dimensional spatial orbital angular momentum holographic technology based on the degrees of freedom of orbital angular momentum and the positional degrees of freedom of reconstructed two-dimensional images in three-dimensional space. In other words, in the three-dimensional spatial orbital angular momentum holography, the acquisition of the target object image requires not only the correct orbital angular momentum state used for decoding, but also the correct spatial position where the object’s image is detected. In addition, we further investigate the three-dimensional spatial orbit angular momentum holographic multiplexing technology and point out that this multiplexing technology can be used for information encryption. Compared with traditional two-dimensional orbital angular momentum holography, three-dimensional spatial orbital angular momentum holography uses an additional degree of freedom. Therefore, the encryption scheme based on three-dimensional spatial orbital angular momentum holographic technology can further improve the security level of information. Our simulation results and experimental results have verified the feasibility of three-dimensional spatial orbit angular momentum holographic technology and three-dimensional spatial orbit angular momentum holographic encryption technology.

Photonic Orbital Angular Momentum for quantum interplaying with atoms and entanglement

Photonic Orbital Angular Momentum (OAM) is becoming a pertinent quantum variable for atom-light interaction, in particular for non-linear interaction which leads to photon entanglement and OAM-entanglement. With two 4-levels atomic schemes, we show that Four Wave Mixing addressed by vortex beams leads to very different OAM-entanglement especially for large OAM values.

Photonic Orbital Angular Momentum for quantum interplaying with atoms and entanglement

Photonic Orbital Angular Momentum (OAM) is becoming a pertinent quantum variable for atom-light interaction, in particular for non-linear interaction which leads to photon entanglement and OAM-entanglement. With two 4-levels atomic schemes, we show that Four Wave Mixing addressed by vortex beams leads to very different OAM-entanglement especially for large OAM values.

Dynamic Micro-Vibration Measurement Based on Orbital Angular Momentum

In this study, we introduce a novel approach for dynamic micro-vibration measurement, employing an Orbital Angular Momentum (OAM) interferometer, where the reference beam is Gaussian (GS) and the measurement beam is OAM. The OAM light reflected back from the target carries information about the target’s vibrations. The interference of the OAM light with Gaussian light generates petal-shaped patterns, and the target’s vibration information can be measured by detecting the rotation angle of these petals. Our proposed method demonstrates enhanced tolerance to misalignment and superior precision. The effects of vibration frequency, CCD frame rates, and Topological Charges (TCs) on measurement accuracy are analyzed thoroughly. Experimental results reveal that the proposed method offers a higher accuracy (up to 22.34 nm) and an extended measurement range of (0–800 cm). These capabilities render our technique highly suitable for applications demanding nanometer-scale resolution in various fields, including precision engineering and advanced optical systems.

Excitation of electron plasma wave by self-focused Laguerre–Gaussian laser beams in axially inhomogeneous plasma: effect of orbital angular momentum of photons

Excitation of electron plasma wave by self-focused Laguerre–Gaussian laser beams in axially inhomogeneous plasma: effect of orbital angular momentum of photons

Spatiotemporal coupling induced controllable orientation of photonic orbital angular momentum at subwavelength scale.

Recently, the emergence of transverse orbital angular momentum (OAM) as a novel characteristic of light has captured substantial attention, and the significance of adjustable OAM orientation has been underscored due to its pivotal role in the interaction between light and matter. In this work, we introduce a novel approach to manipulate the orientation of photonic OAM at subwavelength scales, leveraging spatiotemporal coupling. By tightly focusing a wavepacket containing dual spatiotemporal vortices and a spatial vortex through a high numerical aperture lens, the emergence of intricate coupling phenomena leads to entangled and intricately twisted vortex tunnels. As a consequence, the orientation of spatial OAM deviates from the conventional light axis. Through theoretical scrutiny, we unveil that the orientation of photonic OAM within the focal field is contingent upon the signs of the topological charges in both spatiotemporal and spatial domains. Additionally, the absolute values of these charges govern the precise orientation of OAM within their respective quadrants. Moreover, augmenting the pulse width of the incident light engenders a more pronounced deflection angle of photonic OAM. By astutely manipulating these physical parameters, unparalleled control over the spatial orientation of OAM becomes achievable. The augmented optical degrees of freedom introduced by this study hold considerable potential across diverse domains, including optical tweezers, spin-orbit angular momentum coupling, and quantum communication.

Generating arbitrary non-separable states with polarization and orbital angular momentum of light

We demonstrate an experimental method to generate arbitrary non-separable states of light in two degrees of freedom i.e., polarization and orbital angular momentum (OAM). We observe the intensity distribution corresponding to OAM modes of the light beam by projecting the non-separable state into different polarization states. We further verify the presence of non-separability by measuring the degree of polarization and linear entropy. This classical non-separability can be easily transferred to the quantum domain using spontaneous parametric down-conversion for applications in quantum communication and quantum sensing.

Remote transport of high-dimensional orbital angular momentum states and ghost images via spatial-mode-engineered frequency conversion

The efficient transport and engineering of photonic orbital angular momentum (OAM) lie at the heart of various related classical and quantum applications. Here, by leveraging the spatial-mode-engineered frequency conversion, we realize the remote transport of high-dimensional orbital angular momentum (OAM) states between two distant parties without direct transmission of information carriers. We exploit perfect vortices for preparing high-dimensional yet maximal O AM entanglement. Based on nonlinear sum-frequency generation working with a strong coherent wave packet and a single photon, we conduct the Bell-like state measurements for high-dimensional perfect vortices. We experimentally achieve an average transport fidelity 0.879 ± 0.048 and 0.796 ± 0.066 for a complete set of 3-dimensional and 5-dimensional OAM mutually unbiased bases, respectively. Furthermore, by exploring the full transverse entanglement, we construct another strategy of quantum imaging with interaction-free light. It is expected that, with the future advances in nonlinear frequency conversion, our scheme will pave the way for realizing truly secure high-dimensional quantum teleportation in the upcoming quantum network.

Conservation and non-conservation of photonic angular momentum in a gradient-index fiber

Photonic angular momentum (AM), including the orbital AM (OAM) and spin AM (SAM) of vector vortex beams (VVBs) and partially-coherent VVBs, is analyzed in gradient-index (GRIN) fiber transmission. Photonic spin-orbit interactions (SOIs) occur and the photonic SAM, OAM, and AM (the sum of SAM and OAM) of radially-polarized vortex beams (RVBs) and partially-coherent RVBs (PRVBs) on different planes in the GRIN fiber are simulated. The photonic AM is conserved or not conserved from the SOIs of the RVB and PRVB during GRIN fiber transmission. Simultaneously, the non-conservation characteristics of the photonic AM are regulated by coherence.