Singular optical propagation properties of two types of one-dimensional anti-PT-symmetric periodic ring optical waveguide networks

Two types of one-dimensional(1D)anti-PT-symmetric periodic ring optical waveguide networks,consisting of gain and loss materials,are constructed.The singular optical propagation properties of these networks are investigated.The results show that the system composed of gain materials exhibits characteristics of ultra-strong transmission and bidirectional reflection.Conversely,the system composed of loss materials demonstrates equal transmittance and reflectance at some frequencies.In both the systems,a new type of total reflection phenomenon is observed.When the imaginary part of the refractive indices of waveguide segments is smaller than 10-5,the system shows bidirectional transparency with the transmittance tending to be 1 and reflectivity to be smaller than 10-8 at some bands.When the refractive indices of the waveguide segments are real,the system will be bidirectional transparent at the full band.These findings may deepen the understanding of anti-PT-symmetric optical systems and optical waveguide networks,and possess potential applications in efficient optical energy storage,ultra-sensitive optical filters,ultra-sensitive all-optical switches,integrated optical chips,stealth physics,and so on.

Propagation of a Pearcey beam in uniaxial crystals

An analytical propagation expression of a Pearcey beam in uniaxial crystals orthogonal to the optical axis is derived.The propagations of the Pearcey beam in the tourmaline and the quartz are investigated. The phase distribution and the angular momentum of the Pearcey beam in the tourmaline are also performed. The result shows that the positions of the auto-focusing and the inversion simply relate to the extraordinary refractive index of the crystals. In other words, we can choose the suitable crystals to adjust the positions of auto-focusing and inversion of the Pearcey beam to meet the actual needs.

Propagation properties and radiation force of circular Airy Gaussian vortex beams in strongly nonlocal nonlinear medium

We study the abruptly autofocusing and autodefocusing properties of the circular Airy Gaussian vortex(CAi GV)beams in strongly nonlocal nonlinear medium for the first time through numerical simulations.The magnitude of topological charges and the position of the vortex could change not only the light spot pattern but also the intensity contrast.Meanwhile,we can change the position of the autofocusing and autodefocusing planes by changing the parameter of the incident beam.Furthermore,we can control the peak intensity contrast through choosing properly the truncation factor.As for the radiation force,we study the gradient and the scattering forces of CAi GV beams on Rayleigh dielectric sphere.Our analyses demonstrate that the radiation force can be enhanced by choosing proper parameters of CAi GV beams.

Nonparaxial propagation properties of the chirped Airy Gaussian vortex beams in uniaxial crystals orthogonal to the optical axis

In this article, we investigate the nonparaxial propagation properties of the chirped Airy Gaussian vortex（CAiGV）beams in uniaxial crystals orthogonal to the optical axis analytically and numerically. We discuss how the linear chirp parameters, the quadratic chirp parameters, and the Gaussian factors influence the nonparaxial propagation dynamics of the CAiGV beams. The intensity, the energy flow, the beam center, and the angular momentum of the CAiGV beams are deeply investigated. It is shown that the Gaussian factors have a great effect on the intensity and the centroid positions of the CAiGV beams. With the Gaussian factors increasing, the intensity of CAiGV beams decreases rapidly. The main lobes of the transverse intensity distribution of the CAiGV beams are similar to triangles.

Propagation properties of the chirped Airy–Gaussian vortex electron plasma wave

We introduce a new class of the chirped Airy–Gaussian vortex electron plasma(CAiGVEP)wave which constitutes the exact and continuous transition modes between the chirped Airy vortex and the chirped Gaussian vortex electron plasma wave.The intensity,the phase,and the angular momentum density flow of the CAiGVEP wave are discussed under different distribution factors and different chirp modes.

Propagation properties of chirped Airy vortex beams with x-polarization through uniaxial crystals

The propagation dynamics of a chirped Airy vortex（CAiV） beam with x-polarization in uniaxial crystals orthogonal to the optical axis is studied analytically and numerically. The effect of the ratio of extraordinary and ordinary refractive indices, the chirp parameter, as well as the propagation distance is analyzed, which shows that the focused position of the CAi V beams can be controlled through changing the ratio of the extraordinary and ordinary refractive indices. In addition,with the propagation distance increasing, the asymmetry of the intensity and the angular momentum of the CAi V beam during propagation becomes much more visible. The variation of the chirp parameters can change the attenuation velocity of the vortex as well.

Nonparaxial propagation of radially polarized chirped Airy beams in uniaxial crystal orthogonal to the optical axis

The nonparaxial propagation of radially polarized chirped Airy beams(RPCAiBs) in uniaxial crystal orthogonal to the optical axis is analytically studied. The effects of the first and the second order chirp factors, and the ratio of the extraordinary refractive index to the ordinary refractive index on the nonparaxial evolution of RPCAi Bs in different observation planes are investigated in detail. The results show that when one parameter changes, different components behave differently, and even the same component has various behavior in different directions. The initial slope of RPCAi Bs in the x-direction varies more with the first order chirp factor than that in the y-direction. Meanwhile, with the second order chirp factor becoming larger, the depth of the focus of the y-component in the x-direction decreases while that in the y-direction has no difference. In addition, the different ratios of the extraordinary refractive index to the ordinary refractive index change the difference of the depth of the focus between the x-and the y-components.

Propagation properties of radially polarized Pearcey–Gauss vortex beams in free space

We investigate a family of radially polarized Pearcey–Gauss vortex beams(RPPGVBs),obtain the general propagation expressions of an RPPGVB,and study the intensity distribution,phase pattern,spin currents as well as the orbital currents when the RPPGVB propagates in free space.The focal plane and the intensity of the focal point can be adjusted by changing the position of the vortex and the scaling factors.We also investigate how the waist size influences the propagation properties.

Extraordinary characteristics for one-dimensional parity-time-symmetric periodic ring optical waveguide networks

In this paper, we design a one-dimensional （1D） parity-time-symmetric periodic ring optical waveguide network （PTSPROWN） and investigate its extraordinary optical characteristics. It is found that quite different from traditional vacuum/dielectric optical waveguide networks, 1D PTSPROWN cannot produce a photouic ordinary propagation mode, but can generate simultaneously two kinds of photonic nonpropagation modes： attenuation propagation mode and gain propagation mode. It creates neither passband nor stopband and possesses no photonic band structure. This makes 1D PTSPROWN possess richer spontaneous PT-symmetric breaking points and causes interesting extremum spontaneous PT-symmetric breaking points to appear, where electromagnetic waves can create ultrastrong extraordinary transmission, reflection, and localization, and the maximum can arrive at 6.6556 × 10^12 and is more than 7 orders of magnitude larger than the results reported previously. 1D PTSPROWN may possess potential in designing high-efficiency optical energy saver devices, optical amplifiers, optical switches with ultrahigh monochromaticity, and so on.

Iodine ion modification enables Ag nanowire film with improved carrier transport properties and stability as high-performance transparent conductor

Ag nanowire(NW)film is the promising next generation transparent conductor.However,the residual long-chain polyvinylpyrrolidone(PVP,introduced during the synthesis of Ag NWs)layer greatly deteriorates the carrier transport capability of the Ag NW film and as well its long-term stability.Here,we report a one-step I−ion modification strategy to completely replace the PVP layer with an ultrathin,dense layer of I^(−)ions,which not only greatly diminishes the resistance of the Ag NW film itself and that at interface of the Ag NW film and a functional layer(e.g.,a current collect electrode)but also effectively isolates the approaching of corrosive species.Consequently,this strategy can simultaneously improve the carrier transport properties of the Ag NW film and its long-term stability,making it an ideal electric component in diverse devices.For example,the transparent heater and pressure sensor made from the I^(−)-wrapped Ag NW film,relative to their counterparts made from the PVP-wrapped Ag NW film,deliver much improved heating performance and pressure sensing performance,respectively.These results suggest a facile post treatment approach for thin Ag NW film with improved carrier transport properties and long-term stability,thereby greatly facilitating its downstream applications.

Generation and control of dynamically tunable circular Pearcey beams with annular spiral-zone phase

Light-field shaping technology plays an important role in optics and nanophotonics. For instance, the spatially structured light field, which exhibits characteristic features in complex phases, light intensity, and polarization, is crucial to understanding new physical phenomena and exploring practical applications. Herein, we propose and demonstrate a new class of tunable circular Pearcey beams(TCPBs) by imposing the annular spiral-zone phase(ASZP). Through experiments, we used a spatial light modulator to generate TCPBs based on their spiral phase distribution, and numerically analyzed the generation and control of the beams with unusual autofocusing and self-rotating dynamics. ASZP is a general term for complex phases composed of the spiral phase,equiphase, and radial phase. TCPB typically exhibits dynamical properties, including abrupt autofocusing, automatic generation of optical bottles, and self-rotation of the beam pattern, during propagation. Besides, the number of generated optical bottles can be modulated by the superposition mode of ASZP and the number of subphases. We found that an inappropriate superposition mode leads to distortion, and we analyzed the underlying mechanism. Potential applications of TCPBs in optical manipulation are also discussed, presenting an exemplary role desired for light-field manipulation.

Novel dental implant modifications with two-staged double benefits for preventing infection and promoting osseointegration in vivo and in vitro

Peri-implantitis are a major problem causing implant failure these days.Accordingly,anti-infection during the early stage and subsequent promotion of osseointegration are two main key factors to solve this issue.Micro-arc oxidation(MAO)treatment is a way to form an oxidation film on the surface of metallic materials.The method shows good osteogenic properties but weak antibacterial effect.Therefore,we developed combined strategies to combat severe peri-implantitis,which included the use of a novel compound,PD,comprising dendrimers poly(amidoamine)(PAMAM)loading dimethylaminododecyl methacrylate(DMADDM)as well as MAO treatment.Here,we explored the chemical properties of the novel compound PD,and proved that this compound was successfully synthesized,with the loading efficiency and encapsulation efficiency of 23.91%and 31.42%,respectively.We further report the two-stage double benefits capability of PD+MAO:(1)in the first stage,PD+MAO could decrease the adherence and development of biofilms by releasing DMADDM in the highly infected first stage after implant surgery both in vitro and in vivo;(2)in the second stage,PD+MAO indicated mighty anti-infection and osteoconductive characteristics in a rat model of peri-implantitis in vivo.This study first reports the two-staged,double benefits of PD+MAO,and demonstrates its potential in clinical applications for inhibiting peri-implantitis,especially in patients with severe infection risk.

Sensitive and Selective Determination of Cu^(2+) Using Self-Assembly of 4-Mercaptobenzoic Acid on Gold Nanoparticles

Cu^(2+)is a bio-accumulative and toxic environmental pollutant,so its sensitive and selective detection is of great importance.In this work,gold nanoparticles were electrochemically deposited on fluorine-doped tin oxide and characterized by scanning electron microscope and cyclic voltammetry.4-Mercaptobenzoic acid(4-MBA),which contained carboxyl chelator,was self-assembled on the surface of gold nanoparticles through S-Au bond.The strong chelation of Cu^(2+)with 4-MBA formed a stable Cu^(2+)-4-MBA complex,which was confirmed by energy-dispersive X-ray spectroscopy.Square wave voltammetry was applied to determine the concentration of Cu^(2+).Under optimized condition,the oxidation peak current was proportional to the concentration of Cu^(2+)in the range of 10-1500 nM with limit detection of 8 nM.The proposed electrochemical sensor showed excellent selectivity towards Cu^(2+).In addition,the applicability of the developed sensor was evaluated by determin-ing the concentrations of Cu^(2+)in river water samples,which were consistent with the results of inductively coupled plasma mass spectroscopy.

Resistance potential of soil bacterial communities along a biodiversity gradient in forest ecosystems

Higher biodiversity is often assumed to be a more desirable scenario for maintaining the functioning of ecosystems,but whether species-richer communities are also more disturbance-tolerant remains controversial.In this study,we investigated the bacterial communities based on 472 soil samples from 28 forests across China with associated edaphic and climatic properties.We developed two indexes(i.e.,community mean tolerance breadth[CMTB]and community mean response asynchrony[CMRA])to explore the relationship between diversity and community resistance potential.Moreover,we examined this resistance potential along the climatic and latitudinal gradients.We revealed that CMTB was significantly and negatively related to species richness,resulting from the changes in balance between relative abundances of putative specialists and generalists.In comparison,we found a unimodal relationship between CMRA and richness,suggesting that higher biodiversity might not always lead to higher community resistance.Moreover,our results showed differential local patterns along latitude.In particular,local patterns in the northern region mainly followed general relationships rather than those for the southern forests,which may be attributed to the differences in annual means and annual variations of climate conditions.Our findings highlight that the community resistance potential depends on the composition of diverse species with differential environmental tolerance and responses.This study provides a new,testable evaluation by considering tolerance breadth and response asynchrony at the community level,which will be helpful in assessing the influence of disturbance under rapid shifts in biodiversity and species composition as a result of global environmental change.

Bottom-up fabrication of three-dimensional nanoporous gold from Au nanoparticles using nanowelding

Three-dimensional(3D)nanoporous gold(NPG)shows promising applications in various fields.However,its most common fabrication strategy(i.e.,dealloying)faces the problems of high energy consumption,resource waste,the use of corrosive solvent,and residue of the sacrificial component.Here,we report a general bottom-up nanowelding strategy to fabricate high-purity NPG from Au nanoparticles(NPs),accomplished via interfacial self-assembly of the Au NPs into monolayer Au NP film,its subsequent layer-by-layer transfer onto a solid substrate,and direct current(DC)nanowelding.We show that the DC nanowelding process can gradually evolve the layered Au NP film into NPG at low temperatures within 10 s,while not damaging their spherical structure.This is because during the nanowelding,electrons are preferred to be localized at the high-resistance NP/NP junctions,whose electrostatic repulsion in turn strengthens their surface atom diffusion to initiate a mild solid-state diffusion nanowelding.Furthermore,when using differently sized Au NPs as the starting building blocks,this strategy allows readily tuning the thickness,ligament size,and pore size,thereby offering great flexibility to create functional porous nanomaterials,e.g.,electrocatalyst for methanol electrooxidation.Surely,low-temperature nanowelding can play a role for the production of diverse nanoporous materials from other NPs beyond Au NPs.