Average capacity and bit error rate of vortex gamma beams propagating in non-Kolmogorov atmospheric turbulence.

In recent years, free-space optical communication based on various vortex beams has gained significant attention due to its high channel capacity and low bit error rate (BER). To investigate a novel type of vortex beam (termed as gamma beam) and its application in free-space optical communication (FSO), a comprehensive analysis of its transmission performance in weak-to-strong non-Kolmogorov turbulence has been conducted for the first time. Based on the extended Rytov method, the propagation behaviors of the gamma beam via weak-to-strong non-Kolmogorov turbulent atmosphere is explored, revealing that gamma beams may outperform LG beams and HyGG beams in certain short links.

Fisher information of orbital angular momentum quantum states in atmospheric turbulence.

Free-space optical communication based on orbital angular momentum (OAM) offers advantages such as high security, large information capacity, and high-speed transmission. However, turbulence can induce random perturbations to the wavefront, thereby affecting communication performance. Hence, accurately measuring turbulence intensity is crucial.

Propagation of auto-focusing hypergeometric Gaussian beams along a slant path in oceanic turbulence.

Compared to horizontal transmission, the oceanic dissipation rate and temperature-salinity distribution ratio are no longer constant but vary with depth, imposing greater complexity on oceanic turbulence when beams propagate through a slant path and resulting in more limitations on the performance of underwater wireless optical communication (UWOC) links. This study focuses on investigating the performance, especially the auto-focusing characteristic, of auto-focusing hypergeometric Gaussian (AHGG) beams propagating along slant paths in oceanic turbulence. We theoretically derive the spatial coherence radius and the relative probability of the orbital angular momentum (OAM) mode for AHGG beams passing through such links.

Underwater entanglement propagation of auto-focusing Airy beams.

In underwater wireless optical communication, orbital angular momentum (OAM) states suffer from turbulence distortions. This study aims to investigate the effectiveness of auto-focusing and OAM entanglement of the beams in reducing the turbulence effects. We implement the single-phase approximation and the extended Huygens-Fresnel principle to derive the detection probability of the entangled Airy beams under unstable oceanic turbulence.

Vortex X-wave propagation through von Kármán oceanic turbulence with anisotropy.

Vortex X-waves with coupling effects of orbital angular momentum (OAM) and spatiotemporal invariance are introduced into the research of underwater wireless optical communication systems (UWOCSs). We establish the OAM probability density of vortex X-waves and channel capacity of UWOCS using Rytov approximation and correlation function. Furthermore, an in-depth analysis of OAM detection probability and channel capacity is performed on vortex X-waves carrying OAM in von Kármán oceanic turbulence with anisotropy.

Metasurface-based perfect vortex beams with trigonometric-function topological charge for OAM manipulation.

Topological charge (TC) is generally acknowledged as an important attribute of an optical vortex (OV), which indicates the twisted characterization of the wavefront. In most circumstances, the TC remains constant as an integer or fraction along the azimuthal direction. Herein, by transforming the TCs into the trigonometric functions of the azimuthal angle to tailor the spiral phase distributions, we numerically demonstrate generating perfect vortex beams (PVBs) with sine-function TC based on the all-dielectric geometric metasurfaces, whose unit structure is optimized to an ideal half-wave plate.

Creating perfect composite vortex beams with a single all-dielectric geometric metasurface: erratum.

Erratum to "Creating perfect composite vortex beams with a single all-dielectric geometric metasurface." [Opt. Express30, 40231 (2022)10.

Strong resonance response with ultrahigh quality factor in grating-multilayer systems based on quasi-bound states in the continuum.

Optical bound states in the continuum (BICs) exist in many photonic crystals and periodic structures with a strong resonance and ultrahigh Q factor. Such phenomena can be used in the designs of narrowband transmission filters, lasers, and sensors. In this paper, we consider the energy bands of a complex structure consisting of a grating and a multilayer substructure to obtain the position of the BIC in the structure.

Creating perfect composite vortex beams with a single all-dielectric geometric metasurface.

Optical vortex beam carrying orbit angular momentum has been extensively researched and applied recently. Among which a perfect vortex beam (PVB) has attracted much attention owing to its topological charge (TC)-irrelevant intensity profile. However, the morphology singularity, as well as implementation complexity of the PVB tie the degree of freedom for multiplexing.

Adjustable converter of bound state in the continuum basing on metal-graphene hybrid metasurfaces.

The bound state in the continuum (BIC) is widely applied to metamaterial study in order to obtain robust resonance and high quality (Q) factor. In this paper, we propose a metallic metasurface structure that can support double types of BICs, and acquire quasi-BIC state by restructuring each type with a specific approach. Electric field distribution is investigated to explore the physic mechanism behind the evolution of BICs.

Quantum coherence of thermal biphoton orbital angular momentum state and its distribution in non-Kolmogorov atmospheric turbulence.

Quantum coherence has been considered as a resource for quantum information process in recent years. Sharing the quantum resource distantly is a precondition for quantum communication. In this paper, we explore the quantum coherence properties of the prepared state starting from initially incoherent thermal light source.

All-Dielectric Metasurface Lenses for Achromatic Imaging Applications.

Metasurface can use artificial microstructures to manipulate electromagnetic waves more accurately and flexibly. All-dielectric metalens have a wide range of materials and low cost so it has a wide application prospect. Herein, we propose a all-dielectric achromatic metalens built with Si as the structural unit that can operate over a broadband of wavelengths in the visible region.

Evolution of temporal broadening of ultrashort optical pulse propagation in general ocean turbulence.

Theoretical and experimental explorations have demonstrated that both anisotropy and unstable stratification exist in general ocean turbulence. Recent analyses of temporal broadening of ultrashort optical pulses in oceanic turbulence have adopted the assumptions that the propagation path in the direction was isotropic, or turbulent cells are simply premised on circular symmetry in the xy plane. In this paper, circular symmetry of turbulent cells in the xy plane is no longer maintained, and two anisotropic factors describing the anisotropic scales in the xy plane are introduced to study the temporal broadening of ultrashort optical pulses.

Super-resolution imaging based on radially polarized beam induced superoscillation using an all-dielectric metasurface.

Superoscillation is a kind of phenomenon which can generate oscillation faster than the fastest component of a band-limited function. For optics, superoscillation is generated by coherence of low spatial frequency waves. It can bring a localized region named "hot spot", which has a smaller size than the diffraction-limit, and this character has potential applicaions in super-resolution imaging.

Phase correlation arc and universal decay of entangled orbital angular momentum qubit states in atmospheric turbulence.

In this study, we introduce the phase correlation arc of an orbital angular momentum (OAM) beam to investigate the evolution of OAM entanglement. We reveal that the entanglement decay of all OAM states of Laguerre-Gaussian modes in atmospheric turbulence is universal via both numerical predictions and experimental data. A similar evolution law is also theoretically confirmed to exist in Bessel-Gaussian modes.

Terahertz vortex beam generator based on bound states in the continuum.

Vortex beams are playing an increasingly crucial role in wireless optical communications. Traditional vortex beam generators based on spiral phase plates and metasurfaces have a geometric center in real space, which limit their convenience in practical applications. In this work, we propose that the creation of a vortex beam can be achieved by using the bound state in the continuum (BIC) supported by a photonic crystal slab structure.

Quantum-channel capacity of distributing orbital-angular-momentum states for underwater optical quantum communication.

We employ non-diffractive Bessel-Gaussian beams to investigate the effect of oceanic turbulence on quantum communication protocols via behaviors of quantum-channel capacity and trace distance, based on the analytical expression of the phase structure function of an orbital-angular-momentum (OAM) beam in underwater wireless optical communication. Our results show that turbulence conditions with a larger inner-scale and outer-scale factors, higher dissipation rate of kinetic energy, lower dissipation rate of the mean-squared temperature, and smaller temperature-salinity contribution ratio are beneficial to quantum communication performance. Moreover, we show that the distribution protocol may be improved by distributing quantum superposition states instead of OAM eigenstates.

High-performance terahertz vortex beam generator based on square-split-ring metasurfaces.

Generating a vortex beam is a fundamental task due to the potential applications in wireless communication. Here we propose a kind of high-performance terahertz vortex beam generator with several topological numbers based on the square-split-ring metasurfaces. Via the Fabry-Perot resonance effect of the structure, the transmittance of an orthogonal polarization mode could be remarkably enhanced.

Inversion Method Characterization of Graphene-Based Coordination Absorbers Incorporating Periodically Patterned Metal Ring Metasurfaces.

In this paper, we propose a tunable coordinated multi-band absorber that combines graphene with metal-dielectric-metal structures for the realization of multiple toward perfect absorption. The parametric inversion method is used to extract the equivalent impedance and explain the phenomena of multiple-peak absorption. With the change of the Fermi level, equivalent impedances were extracted, and the peculiarities of the individual multiple absorption peaks to change were determined.

Coordinated multi-band angle insensitive selection absorber based on graphene metamaterials.

In this paper, we propose a tunable, multi-band, selective absorber composed of multiple layers. Each layer consisted of SiO/graphene/SiC, and a layer of silver was used as the ground plane of the entire structure. Simulation results show that we can passively and actively coordinate the resonant frequency of the perfect absorption peak by changing the geometric parameters of the array and the Fermi level of the graphene.

Independent tunable multi-band absorbers based on molybdenum disulfide metasurfaces.

In this paper, we theoretically and numerically demonstrate a dual-band independently adjustable absorber comprising an array of stacked molybdenum disulfide (MoS) coaxial nanodisks and a gold reflector that are separated by two dielectric insulating layers. The array plane functionality is explained by the dipole resonances with the MoS nanodisks. As a result, strong absorption is achieved at a wide range of incident angles under TE and TM polarizations.

Wavelength-sensitive PIT-like double-layer graphene-based metal-dielectric-metal waveguide.

A wavelength-sensitive plasmonically induced transparency-like (PIT-like) device consisting of a double-layer graphene-based metal-dielectric-metal (MDM) waveguide is proposed. We initially investigate monolayer graphene sandwiched in the MDM waveguide and utilize the phase-matching equation to explain the reflected resonant wavelength of the transmission spectra. The PIT-like windows in the transmission spectra of double-layer graphene can be achieved by tuning the applied bias voltage on the graphene layer and the distance between the graphene layer and metal substrate.

Strong optical force and its confinement applications based on heterogeneous phosphorene pairs.

We study the plasmonic properties of face-to-face phosphorene pairs, including their optical constraints and optical gradient forces. The symmetric and anti-symmetric plasmonic modes occur due to the strong anisotropic dispersion of phosphorene. Compared with the anti-symmetric mode, the symmetric mode has a stronger optical constraint and much larger gradient force.

Nonclassical correlations of photonic qubits carrying orbital angular momentum through non-Kolmogorov atmospheric turbulence.

We consider the non-horizontal distributions of orbital angular momentum biphotons through free-space atmospheric channels, in which case the non-Kolmogorov turbulent effects shall be considered. By considering the case of initial non-perfect resource, i.e.