Propagation dynamics of self-accelerating second-order Hermite complex-variable-function Gaussian wave packets in a harmonic potential.

This paper investigates the evolutionary dynamics of self-accelerating second-order Hermite complex-variable-function Gaussian (SSHCG) wave packets in a harmonic potential. The periodic variation of the wave packets is discussed via theoretical analysis and numerical simulation. The control variables method is applied to manipulate the distribution factor, cross-phase factor, potential depth, and chirp parameter, enabling the realization of unique propagation dynamics. In three-dimensional models, the SSHCG wave packets exhibit rotational states, featuring butterfly shape, three peaks shape, two polarity shape, elliptical shape, and ring-shaped double-vortex structures. Furthermore, the energy flow and the angular momentum of the wave packets are investigated. Additionally, the performance of the radiation force on a Rayleigh dielectric particle is studied. This investigation results in the emergence of distinct SSHCG wave packet propagation dynamics, and potential applications in optical communications and optical trapping are presented.

Tunable spin splitting of reflected Laguerre-Gaussian beams on controllable metamaterials with anti-PT symmetry.

The intriguing photonic spin Hall effect (PSHE) of reflected Laguerre-Gaussian (LG) beams can be exhibited on the systems with optical anti-parity-time (Anti-PT) symmetry. During the reflection, the left/right circularly polarized (LCP/RCP) components of reflected LG beams are considered. By controlling parameters of the Anti-PT systems, the PSHE of reflected LCP/RCP can be identical and symmetrical with respect to incident-reflected plane (IRP). Due to gain/non-Hermitian effects of designed Anti-PT systems, special PSHE near the strong gain points (SGP) and exceptional points (EPs) can be obtained simulatively. Through analyses in PSHE of reflected LCP on four similar Anti-PT systems, specific conclusions that can even be extended to more general cases. Moreover, simulations of PSHE by simultaneously varying the incident angles * and imaginary/real dielectric constants Im/Re[ε] of the Anti-PT systems, specal PSHE and other novel optical phenomena with real applications can be revealed. So Anti-PT systems not only provide novel ways to regulate the PSHE of reflected LG beams, but also offer possibilities for new optical characteristics of devices.

Hermite-Gaussian-Talbot carpets.

In this Letter, we demonstrate the generation of Hermite-Gaussian-Talbot carpets (HGTC) based on the interference of a Hermite-Gaussian (HG) beam array with constant successive separation (shift). Despite the acceleration of HG beams during propagation, their symmetric structure ensures that the self-imaged carpets are generated in straight lines perpendicular to the propagation direction, at particular distances, multiples of the famous Talbot distance zT. By considering the separation as a multiple or a fraction of the Hermite-Gaussian beam width, the calculated Talbot distance zT is expressed as a function of the beam parameters, such as the Rayleigh length. The same carpets are also observed in planes situated at different fractions of zT, but with different frequency appearances. An interesting feature of these carpets is that the dimension of one cell of the beam array remains constant in each period (period fraction). We believe that such novel, to our knowledge, carpets will be useful in photonics for creating lattices and optical potentials.

Rydberg-atom acceleration by circular Airy laser pulses.

Circular Airy pulsed beams are introduced to significantly optimize the acceleration of neutral Rydberg atoms. Compared with the conventional pulsed Gaussian beams used in the previous report, the circular Airy structure abruptly self-focuses and subsequently propagates with weak diffraction, resulting in a much higher accelerating efficiency for both radial and longitudinal velocities, as well as a longer accelerating range along the propagation axis. The parameter dependencies of the beams on the acceleration are also analyzed.

Spatiotemporal Airyprime complex-variable-function wave packets in a strongly nonlocal nonlinear medium.

A type of circular Airyprime function of complex-variable Gaussian vortex (AFCGV) wave packets in a strongly nonlocal nonlinear medium is introduced numerically, combining the properties of helicity states and abrupt autofocusing. We investigate the effects of the chirp factor, distribution parameter, and decay factor on the AFCGV wave packets in the strongly nonlocal nonlinear medium. Interestingly, by adjusting the distribution parameter, the AFCGV wave packets can exhibit stable rotational motions in various shapes, such as symmetric lobes and doughnuts. In addition, the Poynting vector and the gradient force of the AFCGV wave packets are also discussed. Our research not only explains the theoretical model for controlling AFCGV wave packets but also advances fundamental research on self-bending and autofocusing structured light fields.

Partially coherent Pearcey-Gauss source with hyperbolic sine correlation of the spatial spectrum.

By designing the intricate coherence structure, we are able to create a desired beam profile and trajectory. Our research focus lies on the Fourier plane, specifically emphasizing the coherence of spatial frequencies, and we find it can be seen as a constant system response. A theoretical framework is developed, and experimental studies are conducted to generate a light field of the spatial spectrum with a complex correlation using the pseudo-mode superposition method. We successfully produce partially coherent Pearcey-Gauss beams whose spatial spectrum is hyperbolic sine correlational. Interestingly, these beams maintain the distinctive propagation properties of the Pearcey pattern while exhibiting the remarkable ability to split the mainlobe into two separate lobes.

(3+1)-dimensional Pearcey-Gaussian wave packet with arbitrary velocity driven by flying focus.

The group velocity (GV) modulation of space-time wave packets (STWPs) along the transverse and longitudinal directions in free space is constrained by various factors. To surmount this limitation, a technique called "flying focus" has been developed, which enables the generation of laser pulses with dynamic focal points that can propagate at arbitrary velocities independent of GV. In this Letter, we propose a (3+1)-dimensional Pearcey-Gauss wave packet based on the "flying focus" technique, which exhibits superluminal propagation, transverse focus oscillation, and longitudinal periodic autofocusing. By selecting appropriate parameters, we can flexibly manipulate the position, the size, and the number of focal points- or make the wave packet follow a desired trajectory. This work may pave the way for the advancement of space-time structured light fields.

A paper-based ratiometric fluorescence sensor based on carbon dots modified with Eu3+ for the selective detection of tetracycline in seafood aquaculture water.

Paper-based ratiometric fluorescence sensors are normally prepared using two or more types of fluorescent materials on a paper chip for simple, low-cost and fast detection. However, the choice of multi-step and one-step modifications on the paper chip affects the analytical performance. Herein, a novel paper-based dual-emission ratiometric fluorescence sensor was designed for the selective detection of tetracycline (TC). Carbon dots (CDs) modified with Eu3+ were combined with a sealed paper-based microfluidic chip by two methods: one-step grafting of CDs-Eu3+ on paper and step-by-step grafting of CDs and Eu3+ on paper. The analytical performance was studied and optimized respectively. The red fluorescence of Eu3+ at 450 nm is enhanced and the blue fluorescence of CDs at 617 nm is quenched by energy transfer in the presence of TC. Under optimal conditions, TC is selectively determined in the linear range from 0.1 µM to 100 µM with a detection limit of 0.03 µM by the step-by-step grafting method. In addition, the sealed paper chip could effectively prevent pollution and volatilization from the reagent. This technique has been used to analyze TC in seafood aquaculture water with satisfactory results.

ZnO-CeO2 Hollow Nanospheres for Selective Determination of Dopamine and Uric Acid.

ZnO-CeO2 hollow nanospheres have been successfully synthesized via the hard templating method, in which CeO2 is used as the support skeleton to avoid ZnO agglomeration. The synthesized ZnO-CeO2 hollow nanospheres possess a large electrochemically active area and high electron transfer owing to the high specific surface area and synergistic effect of ZnO and CeO2. Due to the above advantages, the resulting ZnO-CeO2 hollow spheres display high sensitivities of 1122.86 µA mM-1 cm-2 and 908.53 µA mM-1 cm-2 under a neutral environment for the selective detection of dopamine and uric acid. The constructed electrochemical sensor shows excellent selectivity, stability and recovery for the selective analysis of dopamine and uric acid in actual samples. This study provides a valuable strategy for the synthesis of ZnO-CeO2 hollow nanospheres via the hard templating method as electrocatalysts for the selective detection of dopamine and uric acid.

Application of the Electrospinning Technique in Electrochemical Biosensors: An Overview.

Electrospinning is a cost-effective and flexible technology for producing nanofibers with large specific surface areas, functionalized surfaces, and stable structures. In recent years, electrospun nanofibers have attracted more and more attention in electrochemical biosensors due to their excellent morphological and structural properties. This review outlines the principle of electrospinning technology. The strategies of producing nanofibers with different diameters, morphologies, and structures are discussed to understand the regulation rules of nanofiber morphology and structure. The application of electrospun nanofibers in electrochemical biosensors is reviewed in detail. In addition, we look towards the future prospects of electrospinning technology and the challenge of scale production.

Treatment of Coking Wastewater Using Hydrodynamic Cavitation Coupled with Fenton Oxidation Process.

Effective and economical processes for the advanced treatment of coking wastewater were urgently needed to reduce the persistent organic pollutants of external drainage. In the present work, we investigated the degradation of organic pollutants in coking wastewater through IHC/FO (imping stream hydrodynamic cavitation (IHC) coupled with the Fenton oxidation (FO) process) and IHC alone for their feasibility in the advanced treatment of coking wastewater. To select the optimum parameters, attention was paid to the effects of main operation conditions including inlet fluid pressure, medium temperature, initial pH, reaction time, and initial Fe(II) and initial H2O2 concentrations. The results showed that the effects of conditions that need energy to be maintained (such as initial pH and inlet pressure) on the organic pollutant removal efficiency through IHC/FO were less pronounced than those through IHC alone. Moreover, the application of IHC/FO could remove more organic pollutants from coking wastewater than IHC even at an energy-efficient condition. For example, the highest COD removal efficiency of 12.5% was achieved in the IHC treatment at 0.4 MPa, pH 3, and 60 min for the reaction time. In the case of IHC/FO, the maximum COD removal of 33.2% was obtained at pH 7, 0.1 MPa, 12 mmol/L H2O2, and 3 mmol/L Fe2+ after reacting for 15 min. The ultraviolet and visible spectrophotometry (UV-Vis) absorption spectra and gas chromatography and mass spectrometry (GC-MS) analysis further revealed that the kinds and amounts of pollutants (especially those that had benzenes) remaining in water treated through IHC/FO were much fewer and smaller than in water treated through IHC alone. The better performances of IHC/FO than IHC alone were likely related to the more hydroxyl radicals produced through IHC/FO. Taken together, our findings indicate that IHC/FO has great application potential in the advanced treatment of coking wastewater.

Oral host-microbe interactions investigated in 3D organotypic models.

The oral cavity is inhabited by abundant microbes which continuously interact with the host and influence the host's health. Such host-microbe interactions (HMI) are dynamic and complex processes involving e.g. oral tissues, microbial communities and saliva. Due to difficulties in mimicking the in vivo complexity, it is still unclear how exactly HMI influence the transition between healthy status and disease conditions in the oral cavity. As an advanced approach, three-dimensional (3D) organotypic oral tissues (epithelium and mucosa/gingiva) are being increasingly used to study underlying mechanisms. These in vitro models were designed with different complexity depending on the research questions to be answered. In this review, we summarised the existing 3D oral HMI models, comparing designs and readouts, discussing applications as well as future perspectives.

Autofocus properties of astigmatic chirped symmetric Pearcey Gaussian vortex beams in the fractional Schrödinger equation with parabolic potential.

Described by the fractional Schrödinger equation (FSE) with the parabolic potential, the periodic evolution of the astigmatic chirped symmetric Pearcey Gaussian vortex beams (SPGVBs) is exhibited numerically and some interesting behaviors are found. The beams show stable oscillation and autofocus effect periodically during the propagation for a larger Lévy index (0 < α ≤ 2). With the augment of the α, the focal intensity is enhanced and the focal length becomes shorter when 0 < α ≤ 1. However, for a larger α, the autofocusing effect gets weaker, and the focal length monotonously reduces, when 1 < α ≤ 2. Moreover, the symmetry of the intensity distribution, the shape of the light spot and the focal length of the beams can be controlled by the second-order chirped factor, the potential depth, as well as the order of the topological charge. Finally, the Poynting vector and the angular momentum of the beams prove the autofocusing and diffraction behaviors. These unique properties open more opportunities of developing applications to optical switch and optical manipulation.

Generation and control of the circle Olver beams.

The circle Olver beams (COBs) generated by modulation on the basis of a new type of Olver beam are presented numerically and experimentally. The zeroth order COB is the circle Airy beam. We demonstrate auto-focusing of the COBs with both inward and outward accelerations, where the odd order COBs display auto-defocusing while the even order COBs (ECOBs) tend to focus more abruptly. We also explore the effect of the decay factor and the scaling factor on the beams' focusing properties, such as the initial energy distribution, the focusing position, the focusing intensity and the focusing depth, by using the parity mode. In addition, we verify the self-healing property of the COBs. Finally, we set up an experimental platform to implement particle capture and manipulation with the ECOBs. Our results offer practical applications for particle manipulation, laser processing, etc.

Generation and control of the circle Olver beams: erratum.

We have found an error in our work reported in [Opt. Express31(4), 6241 (2023)10.1364/OE.483433], which we correct in this erratum. The authors apologize for this error and emphasize that none of the results are affected by this error.

Singular multi-wavelength and multi-waveband transparencies generated by P T-symmetric dumbbell optical waveguide networks.

In this paper, we investigate the singular multi-wavelength and multi-waveband transparencies generated by P T-symmetric dumbbell optical waveguide networks composed of two materials, and obtain the number regularity for the transparency wavelengths of one-unit-cell system and the general relationships for the transmission and reflection coefficients of multi-unit-cell systems. Consequently, three types of exact transparencies produced by multi-unit-cell systems are found based on the aforementioned formulas: (i)exact multi-wavelength unidirectional or bidirectional transparency as the same as those of one-unit-cell system; (ii)exact multi-wavelength bidirectional transparency at which one-unit-cell system cannot produce exact transparency, generated by adjusting the number of unit cells; (iii)exact multi-wavelength bidirectional transparency at which one-unit-cell system produces exact transparency, also generated by adjusting the number of unit cells. It provides theoretical foundations for developing highly sensitive and multi-wavelength optical filters. On the other hand, we also discover that multi-unit-cell systems can create approximate multi-waveband bidirectional transparencies by adjusting the number of unit cells, which provides scientific support for developing high-performance optical stealth devices.

Evolution and particle trapping dynamics of circular Pearcey-Airy Gaussian vortex beams in tightly focused systems.

This study investigates the propagation and evolution of self-focusing circular Pearcey-Airy Gaussian vortex beams (CPAGVB) through high numerical aperture objective lenses. CPAGVB demonstrates a unique light field distribution compared to the circular Pearcey vortex beam and circular Airy Gaussian vortex beam. By adjusting optical distribution factors, main radii, and off-axis vortex pair positions, a variety of light field structures can be generated, including asymmetric micro-optical bottles, quasi-flat-top beam micro-optical bottles, and dual optical bottles. The particle trapping performance of CPAGVB is examined, revealing a gradient force eight orders of magnitude larger than its scattering force, up to twice the peak gradient force, and 2.5 times the scattering force of CAGVB. Further analysis of lateral power flow density, spin density vector, and total angular momentum distribution at the focal plane unveils the dynamics of particle motion toward the center. The Gouy phase difference under varying main radii reveals two types of normalized spin density vectors, characterized by helical and oscillating distributions. Additionally, the study examines the two-dimensional polarization ellipse distribution at the focal plane, elucidating the formation of central polarization singularities with axial vortices and the impact of peripheral polarization rearrangement on phase singularities. This research advances the comprehension of CPAGVB's distinctive properties and potential applications in micro-optical systems and particle manipulation.

Propagation dynamics of the controllable circular Airyprime beam in the Kerr medium.

In this paper, we study the propagation dynamics of the circular Airyprime beam (CAPB) in the Kerr medium for the first time. We investigate the effects of the astigmatism factor, the chirp factor, and vortices on the CAPB propagating in the Kerr medium. At the same time, we are also introducing a special-shaped Airyprime beam (SAPB) during its propagation. The transmission characteristics of the CAPB and the SAPB in the Kerr medium are compared under identical conditions. Our theoretical results provide additional possibilities for CAPB modulation in the Kerr medium, thereby promising wider applicability of CAPB in various research areas.

Space-time wave packets with both arbitrary transverse and longitudinal accelerations.

The group velocity in the free space of space-time wave packets (STWPs) and light bullets can be flexibly regulated by many advanced strategies; however, these regulations are restricted to only the longitudinal group velocity. In this work, a computational model based on catastrophe theory is proposed, to devise STWPs with both arbitrary transverse and longitudinal accelerations. In particular, we investigate the attenuation-free Pearcey-Gauss STWP, which enriches the family of non-diffracting STWPs. This work may advance the development of space-time structured light fields.

Particle manipulation with twisted circle Pearcey vortex beams.

In this Letter, we present an approach for particle manipulation utilizing twisted circle Pearcey vortex beams. These beams are modulated by a noncanonical spiral phase, which allows for flexible adjustment of rotation characteristics and spiral patterns. Consequently, particles can be rotated around the beam's axis and trapped with a protective barrier to avoid perturbation. Our proposed system can quickly de-gather and re-gather multiple particles, enabling a swift and thorough cleaning of small areas. This innovation opens up new possibilities in particle cleaning and creates a new platform for further study.