Performance analysis of single-focus phase singularity based on elliptical reflective annulus quadrangle-element coded spiral zone plates

Optical vortices generated by the conventional vortex lens are usually disturbed by the undesired higher-order foci,which may lead to additional artifacts and thus degrade the contrast sensitivity. In this work, we propose an efficient methodology to combine the merit of elliptical reflective zone plates(ERZPs) and the advantage of spiral zone plates(SZPs) in establishing a specific single optical element, termed elliptical reflective annulus quadrangle-element coded spiral zone plates(ERAQSZPs) to generate single-focus phase singularity. Differing from the abrupt reflectance of the ERZPs, a series of randomly distributed nanometer apertures are adopted to realize the sinusoidal reflectance. Typically, according to our physical design, the ERAQSZPs are fabricated on a bulk substrate;therefore, the new idea can significantly reduce the difficulty in the fabrication process. Based on the Kirchhoff diffraction theory and convolution theorem, the focusing performance of ERAQSZPs is calculated. The results reveal that apart from the capability of generating optical vortices,ERAQSZPs can also integrate the function of focusing, energy selection, higher-order foci elimination, as well as high spectral resolution together. In addition, the focusing properties can be further improved by appropriately adjusting the parameters, such as zone number and the size of the consisted primitives. These findings are expected to direct a new direction toward improving the performance of optical capture, x-ray fluorescence spectra, and forbidden transition.

Dynamic phase assembled terahertz metalens for reversible conversion between linear polarization and arbitrary circular polarization

If a metalens integrates the circular polarization(CP)conversion function,the focusing lens together with circular-polariz-ing lens(CPL)in traditional cameras may be replaced by a metalens.However,in terahertz(THz)band,the reported metalenses still do not obtain the perfect and strict single-handed CP,because they were constructed via Pancharatnam-Berry phase so that CP conversion contained both left-handed CP(LCP)and right-handed CP(RCP)components.In this paper,a silicon based THz metalens is constructed using dynamic phase to obtain single-handed CP conversion.Also,we can rotate the whole metalens at a certain angle to control the conversion of multi-polarization states,which can simply manipulate the focusing for incident linear polarization(LP)THz wave in three polarization conversion states,in-cluding LP without conversion,LCP and RCP.Moreover,the polarization conversion behavior is reversible,that is,the THz metalens can convert not only the LP into arbitrary single-handed CP,but also the LCP and RCP into two perpen-dicular LP,respectively.The metalens is expected to be used in advanced THz camera,as a great candidate for tradi-tional CPL and focusing lens group,and also shows potential application in polarization imaging with discriminating LCP and RCP.

Terahertz metasurface zone plates with arbitrary polarizations to a fixed polarization conversion

Metasurfaces that can realize the polarization manipulation of electromagnetic waves on the sub-wavelength scale have become an emerging research field.Here,a novel strategy of combining the metasurface and Fresnel zone plate to form a metasurface zone plate is proposed to realize the conversion from nearly arbitrary polarizations to a fixed polarization.Specifically,when one polarized wave is incident on adjacent ring zones constructed by different types of meta-atoms,the transmitted waves generated by odd-numbered and even-numbered ring zones converge at the same focus and superimpose to generate a fixed polarized wave.As function demonstrations,we have designed two types of metasurface zone plates:one is a focused linear polarizer,and the other can convert nearly arbitrary polarized waves into focused circularly polarized waves.The simulated and measured results are consistent with theoretical expectations,suggesting that the proposed concept is flexible and feasible.Our work provides an alternative platform for polarization manipulation and may vigorously promote the development of polarization photonic devices.

Autophagosome activity in macrophage for atherosclerotic plaques in ApoE^-/-mice enhanced by Tiaozhi Tongmai Granules

Objective:Atherosclerosis is the fundamental pathophysiologic component of cardiovascular disease,and Tiaozhi Tongmai Granules show great efficiency in the treatment of the disease.However,the mechanism of Tiaozhi Tongmai Granules is still unclear.In this study,we have combined experiments with network pharmacology to explore the antiatherosclerosis mechanism of Tiaozhi Tongmai Granules.Method:120 male ApoE
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mice were randomly divided into three groups:the model group,Chinese herb group and Atorvastatin group.The model group,Atorvastatin group and Chinese herb group were fed with a high-fat diet,a high-fat diet plus atorvastatin(5.1 mg/kg/d)and a high-fat diet plus Tiaozhi Tongmai Granules(16.5 g/kg/d)for 16 weeks,respectively.Atherogenesis was identified by H&E staining.The colocalization of neutral lipid stain BODIPY and microtubule-associated protein 1 light chain 3(LC3)and the colocalization of BODIPY and lysosomal-associated membrane protein 1(LAMP1)within ApoE
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mice aortic plaques were tested using fluorescence confocal microscopy and the Pearson’s coefficients were calculated.To further explore the anti-atherosclerosis mechanism of Tiaozhi Tongmai Granules,the network pharmacology was used to construct the herb-compound-target network.Results:The size of the aortic lipid plaque in the Chinese herb group and Atorvastatin group were smaller compared with the model group on the 16th week.Compared with the model group on the 16th week,the BODIPY and LC3 colocalization rate,the BODIPY and LAMP1 colocalization rate of the Chinese herb group and Atorvastatin group all presented significant increase in the aortic plaque(P<.001),showing that Tiaozhi Tongmai Granules could enhance autophagosome activity in the macrophage.In the herb-compound-target network,17 active compounds and 27 targets were obtained through literature searching and using LHRI&DAVID Bioinformatics.It was found that 23 targets were correlated with the macrophage.Some of them participated in macrophage inflammatory response,and the other targets could promote/inhibit phagocytosis of the macrophage.It was hypothesized that the active compounds of Tiaozhi Tongmai Granules were acting on these targets and having y the biological effects.Conclusions:In the progression stage of atherosclerosis,Tiaozhi Tongmai Granules can still make the macrophage have higher autophagosome activity,and play a role of anti-atherogenesis.

Tiaozhi Tongmai Granules reduce atherogenesis and promote the expression of ATP-binding cassette transporter A1 in rabbit atherosclerotic plaque macrophages and the liver

Objective:ATP-binding cassette transporter A1(ABCA1)is an integral membrane protein that plays a key role in cellular lipid metabolism,preventing the accumulation of lipids that contribute to the initiation and progression of atherosclerosis.Tiaozhi Tongmai Granules are a Chinese herbal compound that is capable of treating atherosclerosis.This study was designed to explore the potential pharmacological mechanism by which Tiaozhi Tongmai Granules protect against atherosclerosis.Methods:Forty-nine male New Zealand rabbits were randomly divided into seven groups:normal control group,normal diet;model groups 1 and 2:balloon injury and high-fat diet for 6 or 12 weeks;statin groups 1 and 2:balloon injury and high-fat diet plus atorvastatin for 6 or 12 weeks;and Chinese herb groups 1 and 2:balloon injury and high-fat diet plus Tiaozhi Tongmai Granules for 6 or12 weeks.The granules were administered at a dose of 1.14 g/kg/d,with atorvastatin(1.14 mg/kg/d)serving as positive control.Serum lipid profiles and liver function indices were measured.Atherogenesis was viewed after H&E staining and quantified by thickened intimal area percentage and maximal intimal thickness percentage.The ABCA1 protein expression in atherosclerotic plaque macrophages of the common carotid arteries(CCA),thoracic aortae(TA),and liver tissues were observed by immunohistochemical staining and evaluated using mean optical density(OD)value in macrophages and ABCA1-positive hepatocyte number.Results:Compared with model group 1 at week 6,Chinese herb group 1 and statin group 1 displayed significant reductions in total cholesterol(TC)(PZ0.027,0.012)and low-density lipoprotein cholesterol(LDL-C)(PZ0.039,0.028)levels,as well as marked increases in ABCA1-positive hepatocyte numbers(P all<0.001),and only statin group 1 displayed a markedly reducedmaximal intimal thickness percentage in the CCA(P Z 0.018).Compared with model group 2 at week 12,Chinese herb group 2 and statin group 2 all presented significant reductions in TC(P Z 0.011,0.003),LDL-C(P Z 0.017,0.010)and thickened intimal area percentage in the CCA(P Z 0.001,0.022),as well as prominent increases in the ABCA1 OD value of both the CCA(P Z 0.001,0.039)and TA(P Z 0.001,0.025)and positive hepatocyte number(P all<0.001).Chinese herb group 2 had a markedly reduced maximal intimal thickness percentage compared with model group 2(P Z 0.006)and a higher positive hepatocytes number than statin group 2(P Z 0.001).Conclusions:Tiaozhi Tongmai Granules appear to have an anti-atherogenic effect that is most likely mediated by simultaneously upregulating the protein expression of ABCA1 in rabbit atherosclerotic plaque macrophages and in the liver.

Application of S-transform threshold filtering in Anhui experiment airgun sounding data de-noising

As a relatively new method of processing non-stationary signal with high time-frequency resolution, S transform can be used to analyze the time-frequency characteristics of seismic signals. It has the following characteristics: its time-frequency resolution corresponding to the signal frequency, reversible inverse transform, basic wavelet that does not have to meet the permit conditions. We combined the threshold method, proposed the S-transform threshold filtering on the basis of S transform timefrequency filtering, and processed airgun seismic records from temporary stations in "Yangtze Program"(the Anhui experiment). Compared with the results of the bandpass filtering, the S transform threshold filtering can improve the signal to noise ratio(SNR) of seismic waves and provide effective help for first arrival pickup and accurate travel time. The first arrival wave seismic phase can be traced farther continuously, and the Pm seismic phase in the subsequent zone is also highlighted.

Effect of Yiqi Huoxue Decoction on the metabolomics of acute myocardial infarction rats

Objective:To explore the effect of Yiqi Huoxue Decoction on the metabolomics of acute myocardial infarction rats.Method:Left anterior descending coronary artery ligation was used to establish an acute myocardial infarction animal model.The rats were randomly divided into model,perindopril,QishenYiqi Dropping Pill and Yiqi Huoxue Decoction groups and compared with a shamoperation group.Blood metabolite changes were detected by nuclear magnetic resonance metabolomics 7 and 28 days after operation.Metabolite differences between the administration and model groups were analyzed.P-values of the differences in metabolite levels between the drug and model groups were statistically analyzed.Results:Compared with the sham-operation group,there were 22 altered metabolites in the model group identified after 7 days and 15 identified after 28 days.Products of energy,carbohydrate,lipid and amino acid metabolism were the primary metabolites observed in the analyzed samples.Conclusion:After intervention with traditional Chinese medicine,there were clear changes in energy,carbohydrate,lipid and amino acid metabolism that restored the metabolic phenotype to the normal range,thus repairing the damage caused by myocardial infarction.

Full-Stokes metasurface polarimetry requiring only a single measurement

Polarization is crucial in various fields such as imaging,sensing,and substance detection.A compact,fast,and accurate polarization detection device is vital for these applications.Herein,we demonstrate a multifocus metalens for terahertz polarization detection that requires only a single measurement to obtain complete polarization parameters and reconstruct the polarization state of the incident field.The individual subarrays of this metalens convert each of the six polarized components into the same polarization,which in turn links the Stokes parameters to these six foci.The incident linear polarizations and elliptical polarizations are characterized by Stokes parameters and polarization ellipses.Simulations and experimental results show that the scheme can accurately detect the incident polarization with a single measurement.The proposed metasurface polarimetry may find applications in the fields of real-time terahertz detection and integrated optics.

波前可控的全硅太赫兹超构起偏器

直接从非偏振波中产生偏振波并同时操纵波前的超材料器件可用于先进的光学系统.然而,传统的波前可控偏振转换超表面(PCMs)依赖于具有特定偏振状态的入射波,而不是非偏振波.少数经特殊设计的超构起偏器虽然已经从非偏振波中获得了偏振波,但没有同步地实现波前操控.本文报道了基于全硅材料的波前可控的太赫兹超构起偏器,它比传统的超构起偏器和波前可控PCMs具有更高的集成特性.这种太赫兹超构起偏器将特定相位分布融入超构原子的波束干涉中,直接从非偏振太赫兹波产生偏振太赫兹波,并同步实现波前操控,有望为太赫兹波操控领域带来新的影响.

Binary encoding-inspired generation of vector vortex beams

Vortex and vector terahertz(THz)beams with inhomogeneous polarization states have become a considerable hot topic in the last decade due to their important roles in multiplexed wireless data transmission.However,the technical instruments to form and evaluate such beams are rather limited,as they are mainly collected in the visible range.The emergence of coded metasurfaces has reinvigorated the design of functional devices with multiple degrees of freedom.Here,we demonstrate a versatile design inspired by a binary encoding approach for generating off-axis vectorial THz beams on all-silicon metasurfaces.Experimentally,simultaneous manipulation of the encoding method within the orthogonal circularly polarized(CP)channel provides strong support for developing versatility in vector THz beams,including the generation of arbitrary polarization profiles and the directional emission of multiplexed vector vortex beams(VVBs)with specified polarization states.The introduction of the latitudinal polarization control factor guarantees that continuously rotating or independently designed vector polarization profiles can be obtained on a pre-defined focal plane.Subsequently,a universal parametric theoretical model is developed to analyze the evolutionary trend of off-axis VVB in detail.Notably,the proposed monolayer vector metasurface bypasses the requirement of multiple cascaded optical elements,further inducing the advancement of ultra-thin vector THz sources,and also facilitating the generation of vector fields with tailored polarization distributions in 3D space.

Terahertz metasurface polarization detection employing vortex pattern recognition

The manipulation and detection of polarization states play a crucial role in the application of 6G terahertz communication.Nonetheless,the development of compact and versatile polarization detection devices capable of detecting arbitrary polarizations continues to be a challenging endeavor.Here,we demonstrate a terahertz polarization detection scheme by performing mode purity analysis and multidimensional analysis of the transmitted vortex field.The power of the proposed polarization recognition is verified by using three polarization trajectories,including linear polarizations,circular polarizations,and elliptical polarizations.Using the reconstructed complete polarization parameters,the detected polarization states are characterized using polarization ellipses,Poincarésphere,and full-Stokes parameters.The experimental results validate the power of this scheme in polarization detection.This scheme holds promise for applications in polarization imaging and terahertz communication.

All-silicon chiral metasurfaces and wavefront shaping assisted by interference

Chiral metasurfaces have different electromagnetic responses with circularly polarized lights,showing as circular dichroism and optical activity.Here,a novel kind of all-silicon chiral metasurface is proposed by introducing destructive interference between achiral meta-atoms.The maximum value of circular dichroism spectra can reach 0.49.By adding an antireflective layer at the side of the silicon substrate,the maximum circular dichroism reaches 0.54.What is more,the bandwidth of circular dichroism greater than 0.4 reaches 0.15 THz.Two samples are fabricated to verify the feasibility of this scheme,and the experimental results are in good agreement with the simulations.In addition,the proposed scheme can also be used to generate various interesting functions,such as beam control and vortex generator.This flexible and efficient implementation solution of chiral metasurface can bring new ideas to the development of chiral devices in the future.

Terahertz wavefront shaping with multi-channel polarization conversion based on all-dielectric metasurface

Polarization manipulation of electromagnetic wave or polarization multiplexed beam shaping based on metasurfaces has been reported in various frequency bands.However,it is difficult to shape the beam with multi-channel polarization conversion in a single metasurface.Here,we propose a new method for terahertz wavefront shaping with multi-channel polarization conversion via all-silicon metasurface,which is based on the linear shape birefringence effect in spatially interleaved anisotropic meta-atoms.By superimposing the eigen-and non-eigen-polarization responses of the two kinds of meta-atoms,we demonstrate the possibility for high-efficiency evolution of several typical polarization states with two independent channels for linearly polarized waves.The measured polarization conversion efficiency is higher than 70%in the range of 0.9–1.3 THz,with a peak value of 89.2%at 1.1 THz.In addition,when more other polarization states are incident,combined with the integration of sub-arrays,we can get more channels for both polarization conversion and beam shaping.Simulated and experimental results verify the feasibility of this method.The proposed method provides a new idea for the design of terahertz multi-functional metadevices.

Circular dichroism-like response of terahertz wave caused by phase manipulation via all-silicon metasurface

Chiral metasurfaces based on asymmetric meta-atoms have achieved artificial circular dichroism(CD),spin-dependent wavefront control,near-field imaging,and other spin-related electromagnetic control.In this paper,we propose and experimentally verify a scheme for achieving high-efficiency chiral response similar to CD of terahertz(THz)wave via phase manipulation.By introducing the geometric phase and dynamic phase in an all-silicon metasurface,the spin-decoupled terahertz transmission is obtained.The giant circular dichroism-like effect in the transmission spectrum is observed by using a random phase distribution for one of the circular polarization components.More importantly,the effect can be adjusted when we change the area of the metasurface illuminated by an incident terahertz beam.In addition,we also demonstrate the spin-dependent arbitrary wavefront control of the transmitted terahertz wave,in which one of the circularly polarized components is scattered,while the other forms a focused vortex beam.Simulated and experimental results show that this method provides a new idea for spin selective control of THz waves.

Manipulation of polarization conversion and multiplexing via all-silicon phase-modulated metasurfaces

Phase-modulated metasurfaces that can implement the independent manipulation of co-and cross-polarized output waves under circularly polarized[CP]incidence have been proposed.With this,we introduce one particular metasurface composed of meta-atoms with a phase difference of 2π/3 to generate specific elliptically polarized waves under various polarized incidences.Furthermore,a metasurface composed of these above meta-atoms and the meta-atoms with a phase difference of π/3 arranged in a certain rule can realize polarization conversion function between linearly polarized and CP states.The designs shed new light on multifarious optical devices and may further promote the development of metasurface polarization optics.

Broadband and tunable terahertz absorption via photogenerated carriers in undoped silicon

Terahertz absorbers based on doped silicon have achieved broadband and high-efficiency absorption due to their high concentration of carriers.However,their tunable performance is obviously insufficient.Here,we propose a new scheme for active terahertz absorption based on undoped silicon with a metamaterial antireflection layer,which realizes both strong absorption and ultrahigh modulation depth.Benefiting from the weak absorption and high transmission of undoped silicon for 1064-nm continuous wave,uniformly distributed carriers across the entire thickness of the absorber are excited,and efficient free carrier absorption of the terahertz wave is obtained.We use only a 500-μm thick absorber and achieve absorption greater than 90%in the range of 0.58 to 1.92 THz,with a peak value of 99%.More important,the absorber can be switched between two working states of nonabsorption and high-efficiency absorption by changing the pump power,which means the modulation depth reaches 100%.This simple and high-performance implementation scheme provides a new idea for the design of terahertz tunable absorbers.

Generation of X-ray vortex with ultra-long depth of focus using axial line-focused spiral zone plates

We propose axial line-focused spiral zone plates （ALFSZPs） for generating tightly focused X-ray vortex beams with ultra-long depth of focus （DOF） along the propagation direction. In this typical design, compared with the conventional spiral zone plates （SZPs） under the same numerical aperture （NA）, the DOF of ALFSZPs has been extended to an ultra-length by optimizing the corresponding parameters. Besides, it also exhibits lower side lobes and smaller dark cores in the whole focus volume. The diameters of dark cores increase as the topological charge value increases.