Toroidal Dipole BIC-Driven Highly Robust Perfect Absorption with a Graphene-Loaded Metasurface.

Achieving perfect absorption in few-layer two-dimensional (2D) materials plays a crucial role in applications such as optoelectronics and sensing. However, the underlying mechanisms of all reported works imply a strongly inherent dependence of the central wavelength on the structural parameters. Here, we propose a structure-parameter-deviation immune method for achieving perfect absorption at any desired wavelength by harnessing the toroidal dipole-bound state in the continuum (TD BIC). We experimentally demonstrate the versatile design with a monolayer-graphene-loaded compound grating structure. Such a TD BIC built upon the TE31 mode allows for the transition from BIC to quasi-BIC without breaking the structural symmetry, enabling the stable resonance wavelength while tailoring the quality factors via variation of the gap distance. Comparison with traditional literature further reveals the superiority of our method in realizing highly robust perfect absorption, with a wavelength stability ratio of >15. Remarkably, this approach can be straightforwardly applied to other 2D materials.

Continuous-Spectrum-Polarization Recombinant Optical Encryption with a Dielectric Metasurface.

The Jones matrix, with eight degrees of freedom (DoFs), provides a general mathematical framework for the multifunctional design of metasurfaces. Theoretically, the maximum eight DoFs can be further extended in the spectrum dimension to endow unique encryption capabilities. However, the topology and intrinsic spectral responses of meta-atoms constrains the continuous engineering of polarization evolution over wavelength dimension. In this work, a forward evolution strategy to quickly establish the mapping relationships between the solutions of the dispersion Jones matrix and the spectral responses of meta-atoms is reported. Based on the eigenvector transformation method, arbitrary conjugate polarization channels over the continuous-spectrum dimension are successfully reconstructed. As a proof-of-concept, a silicon metadevice is demonstrated for optical information encryption transmission. Remarkably, the arbitrary combination forms of polarization and wavelength dimension increase the information capacity (210 ), and the measured polarization contrasts of the conjugate polarization conversion are >94% in the entire wavelength range (3-4 µm). It is believed that the proposed approach will benefit secure optical and quantum information technologies.

Polychromatic full-polarization control in mid-infrared light.

Objects with different shapes, materials and temperatures can emit distinct polarizations and spectral information in mid-infrared band, which provides a unique signature in the transparent window for object identification. However, the crosstalk among various polarization and wavelength channels prevents from accurate mid-infrared detections at high signal-to-noise ratio. Here, we report full-polarization metasurfaces to break the inherent eigen-polarization constraint over the wavelengths in mid-infrared. This recipe enables to select arbitrary orthogonal polarization basis at individual wavelength independently, therefore alleviating the crosstalk and efficiency degradation. A six-channel all-silicon metasurface is specifically presented to project focused mid-infrared light to distinct positions at three wavelengths, each with a pair of arbitrarily chosen orthogonal polarizations. An isolation ratio of 117 between neighboring polarization channels is experimentally recorded, exhibiting detection sensitivity one order of magnitude higher than existing infrared detectors. Remarkably, the high aspect ratio ~30 of our meta-structures manufactured by deep silicon etching technology at temperature -150 °C guarantees the large and precise phase dispersion control over a broadband from 3 to 4.5 µm. We believe our results would benefit the noise-immune mid-infrared detections in remote sensing and space-to-ground communications.

Selective Enhancement of Photoresponse with Ferroelectric-Controlled BP/In2 Se3 vdW Heterojunction.

Owing to the large built-in field for efficient charge separation, heterostructures facilitate the simultaneous realization of a low dark current and high photocurrent. The lack of an efficient approach to engineer the depletion region formed across the interfaces of heterojunctions owing to doping differences hinders the realization of high-performance van der Waals (vdW) photodetectors. This study proposes a ferroelectric-controlling van der Waals photodetector with vertically stacked two-dimensional (2D) black phosphorus (BP)/indium selenide (In2 Se3 ) to realize high-sensitivity photodetection. The depletion region can be reconstructed by tuning the polarization states generated from the ferroelectric In2 Se3 layers. Further, the energy bands at the heterojunction interfaces can be aligned and flexibly engineered using ferroelectric field control. Fast response, self-driven photodetection, and three-orders-of-magnitude detection improvements are achieved in the switchable visible or near-infrared operation bands. The results of the study are expected to aid in improving the photodetection performance of vdW optoelectronic devices.

Polarization-controlled varifocal metalens with a phase change material GSST in mid-infrared.

Detection of aldehyde carbonyl radiation plays an essential role in guaranteeing the safety of fried food. However, the radiation of low-content aldehyde carbonyl is always weak and includes polarized light. Focusing the weak radiation with polarization-sensitive configurations provides an efficient way to improve the signal-to-noise ratio of detection. The advent of dynamic metasurfaces based on phase-change materials (PCMs) have demonstrated superiorities over their traditional counterparts in tunability and miniaturization. In this paper, we propose two reflected varifocal metasurfaces, which combine Ge2Sb2Se4Te1 (GSST) with two materials that have close optical constants with amorphous and crystalline GSST. The first one realizes a four-spot focal system with linearly-polarized incidence based on polarization multiplexing. It adds a new polarization degree of freedom compared with traditional varifocal metasurfaces. Compared with traditional spatial-multiplexing method, our second metasurface enables the independent control of the polarization and phase profiles of circularly-polarized light. Remarkably, it reduces energy loss and crosstalk. We believe the novel scenarios of combing GSST with similar materials provide a new direction for tunable metasurfaces based on PCMs.

The Impact of Manufacturing Imperfections on the Performance of Metalenses and a Manufacturing-Tolerant Design Method.

Metalenses play an important role in optoelectronic integrated devices, given their advantages in miniaturization and integration. Due to its high aspect ratio subwavelength structure, fabricating metalenses requires a high-level dry etching technology. Consequently, structure deformation of the metalens will exist if the etching process of the material is not mature enough, which will impair the metalens' performance. In this paper, a polarization-independent InP dielectric metalens is designed to focus the incident light from air into the substrate, which is used for monolithically integrating with the InGaAs/InP photodetector in the future. Subsequently, with the simulation method, we investigated the impact of the structure deformation on the metalens' performance, which was found in our InP dry etching process development. We have found that the sidewall slope and aspect ratio-dependent etching effect greatly impaired the focusing efficiency because of the phase modulation deviation. To solve this problem, we proposed a manufacturing-tolerant design method, which effectively improved the performance of the device with structural deformation. Our work is instructive for developing metalenses and can accelerate their integration application.

Photonic slide rule with metasurfaces.

As an elementary particle, a photon that carries information in frequency, polarization, phase, and amplitude, plays a crucial role in modern science and technology. However, how to retrieve the full information of unknown photons in an ultracompact manner over broad bandwidth remains a challenging task with growing importance. Here, we demonstrate a versatile photonic slide rule based on an all-silicon metasurface that enables us to reconstruct incident photons' frequency and polarization state. The underlying mechanism relies on the coherent interactions of frequency-driven phase diagrams which rotate at various angular velocities within broad bandwidth. The rotation direction and speed are determined by the topological charge and phase dispersion. Specifically, our metasurface leverages both achromatically focusing and azimuthally evolving phases with topological charges +1 and -1 to ensure the confocal annular intensity distributions. The combination of geometric phase and interference holography allows the joint manipulations of two distinct group delay coverages to realize angle-resolved in-pair spots in a transverse manner- a behavior that would disperse along longitudinal direction in conventional implementations. The spin-orbital coupling between the incident photons and vortex phases provides routing for the simultaneous identification of the photons' frequency and circular polarization state through recognizing the spots' locations. Our work provides an analog of the conventional slide rule to flexibly characterize the photons in an ultracompact and multifunctional way and may find applications in integrated optical circuits or pocketable devices.

Recent Progress in Improving the Performance of Infrared Photodetectors via Optical Field Manipulations.

Benefiting from the inherent capacity for detecting longer wavelengths inaccessible to human eyes, infrared photodetectors have found numerous applications in both military and daily life, such as individual combat weapons, automatic driving sensors and night-vision devices. However, the imperfect material growth and incomplete device manufacturing impose an inevitable restriction on the further improvement of infrared photodetectors. The advent of artificial microstructures, especially metasurfaces, featuring with strong light field enhancement and multifunctional properties in manipulating the light-matter interactions on subwavelength scale, have promised great potential in overcoming the bottlenecks faced by conventional infrared detectors. Additionally, metasurfaces exhibit versatile and flexible integration with existing detection semiconductors. In this paper, we start with a review of conventionally bulky and recently emerging two-dimensional material-based infrared photodetectors, i.e., InGaAs, HgCdTe, graphene, transition metal dichalcogenides and black phosphorus devices. As to the challenges the detectors are facing, we further discuss the recent progress on the metasurfaces integrated on the photodetectors and demonstrate their role in improving device performance. All information provided in this paper aims to open a new way to boost high-performance infrared photodetectors.

Mid-infrared polarization-controlled broadband achromatic metadevice.

Metasurfaces provide a compact, flexible, and efficient platform to manipulate the electromagnetic waves. However, chromatic aberration imposes severe restrictions on their applications in broadband polarization control. Here, we propose a broadband achromatic methodology to implement polarization-controlled multifunctional metadevices in mid-wavelength infrared with birefringent meta-atoms. We demonstrate the generation of polarization-controlled and achromatically on-axis focused optical vortex beams with diffraction-limited focal spots and switchable topological charge (L ∥ = 0 and L ⊥ = 2). Besides, we further implement broadband achromatic polarization beamsplitter with high polarization isolation (extinction ratio up to 21). The adoption of all-silicon configuration not only facilitates the integration with CMOS technology but also endows the polarization multiplexing meta-atoms with broad phase dispersion coverage, ensuring the large size and high performance of the metadevices. Compared with the state-of-the-art chromatic aberration-restricted polarization-controlled metadevices, our work represents a substantial advance and a step toward practical applications.

Selectively thermal radiation control in long-wavelength infrared with broadband all-dielectric absorber.

Artificial control of the thermal radiation is of growing importance to fundamental science and technological applications, ranging from waste heat recovery to thermophotovoltaics. Nanophotonics has been proven to be an efficient approach to manipulate the radiation. In comparison with structures utilizing planar subwavelength scale lithography, in this paper, we propose a cascaded all-dielectric multilayer structure to selectively manipulate the thermal radiation characteristics in long-wavelength infrared (LWIR). The broadband emissivity in non-atmospheric windows (6.3-7.5 µm) can reach 0.95 and the average absorption rate is below 3% in atmospheric windows (8-14 µm). The multilayer structure is insensitive to the polarization of the incident waves and maintains a good rectangular absorptivity curve even with large oblique incidence angle at 45 degrees. The outstanding properties of the nanostructures promise various applications in infrared sensing and thermal imaging.

Proteomics Analysis Identifies IRSp53 and Fascin as Critical for PRV Egress and Direct Cell-Cell Transmission.

Pseudorabies virus (PRV) has been widely used as a live trans-synaptic tracer for mapping neuronal circuits. Systematically identifying mature PRV virion proteomes and defining co-purified host proteins are necessary to fully understand the detailed mechanism underlying PRV transmission processes. Here, a PRV virion purification strategy based on sorting with flow cytometry is developed and the mature extracellular and intracellular PRV virion proteomes using LC coupled with MS/MS are characterized. In addition to viral proteins, a large number of host proteins are also identified, including proteins related to actin cytoskeletal dynamics and membrane protrusion. How many of these host proteins are true virion components are unknown and the majority of these may not be. Through functional analysis, it is found that IRSp53 and fascin are critical for the egress process and play a role in direct cell-cell transmission. Moreover, it is shown that CDC42 and Rac1 are also involved in the production of mature extracellular virions. The results suggest that the formation of the filopodia-like cytoskeleton and the rearrangement of the membrane, which are both associated with IRSp53 and fascin, may be important for the transmission of viruses used in neuronal tracing.

High efficiency focusing vortex generation and detection with polarization-insensitive dielectric metasurfaces.

The optical vortex beam with an orbital angular momentum, featuring a doughnut intensity distribution and a helically structured wavefront, has received extensive attention due to its applications in nanoparticle manipulation and optical communications. In this paper, we propose high-efficiency polarization-independent vortex beam generators which are capable of transforming the arbitrarily polarized plane wave into a focusing optical vortex beam and an abruptly focusing airy vortex beam. Besides, based on holographic metasurfaces, we provide a general design scheme for detecting the topological charges. With such a design strategy, multichannel topological charge resolved devices are demonstrated, which successfully implement the detection of the topological charges from -2 to 2. The metasurfaces designed with a simple and effective method in light manipulation promise photonic applications in secure communications and other related areas.

Quantitative proteomics study of host response to virulent and attenuated pseudorabies virus infection in mouse brain.

Bartha, the pseudorabies virus (PRV) vaccine strain, is widely used in studies of neuronal circuit-tracing, due to its attenuated virulence and retrograde spreading. However, we know little regarding the molecular mechanisms of PRV infection and spreading between structurally connected neurons. In this study, we systematically analyzed the host brain proteomes after acute infection with PRV, attempting to identified the proteins involved in the processes. Mice were injected with PRV-Bartha and PRV-Becker (PRV-Bartha's wild-type parent strain) in the olfactory system, the proteomes of the brain and synaptosome were analyzed and compared at various infection intervals using mass spectrometry-based proteomics techniques. In all, we identified >100 PRV-infection regulated proteins at the whole-tissue level and the synaptosome level. While at whole-tissue level, bioinformatics analyses mapped most of the regulations to the inflammation pathways, at the synaptosome level, most of those to synaptic transmission, cargo transport and cytoskeleton organization. We established regulated protein networks demonstrating distinct cellular regulation pattern between the global and the synaptosome levels. Moreover, we identified a series of potentially PRV-strain-specific regulated proteins with diverse biological functions. This study may provide new clues for molecular mechanisms for PRV infection and spread.

Polarization-independent metalens constructed of antennas without rotational invariance.

We propose a novel approach to designing an ultrathin polarization-independent metalens (PIM) by utilizing antennas without rotational invariance. Two arrays of nanoblocks are elaborately designed to form the super cell of the PIM, which are capable of focusing right-handed circularly polarized and left-handed circularly polarized lights. With such a strategy, the PIM is able to achieve polarization-independent focusing, since the light with any polarization can be treated as a combination of the two orthogonal ones. A theoretical analysis based on the Jones vector is proposed to detailedly explore the underlying physics. The polarization-independent characteristic of the designed PIM is also demonstrated by utilizing finite difference time domain simulations. Moreover, polarization-independent focusing can be achieved within a wavelength range of 400 nm. These results can deepen our understanding of polarization-independent focusing and provide a new method for designing ultrathin polarization-independent devices.

Annihilating optical angular momentum and realizing a meta-waveplate with anomalous functionalities.

Manipulating the polarization states of electromagnetic waves, a fundamental issue in optics, has attracted intense attention. However, most of the reported devices are either so bulky or with specific functionalities. Here we propose a conceptually new approach to design an ultra-thin meta-waveplate (MWP) with anomalous functionalities. By elaborately designing the structural units of the metasurface, the incident right circular polarized (CP) light carrying spin angular momentum can be coupled into two surface plasmon modes with opposite orbital angular momenta which interaction with each other in the near-field, degenerating to a linear polarized (LP) light in the far-filed. The incoming spin angular momentum is annihilated and the designed MWP can function as a quarter-waveplate. However, compared with the conventional quarter-waveplates, our designed MWP owns the unidirectional function (only converting CP light to LP light) with a certain output polarization angle, which provides an extra degree of freedoms in controlling the polarization. Moreover, the designed MWP can function as a chiral material and exhibiting optical rotation properties within a broad bandwidth.

Morphology Evolution of Polymer Blends under Intense Shear During High Speed Thin-Wall Injection Molding.

The morphology evolution under shear during different processing is indeed an important issue regarding the phase morphology control as well as final physical properties of immiscible polymer blends. High-speed thin wall injection molding (HSTWIM) has recently been demonstrated as an effective method to prepare alternating multilayered structure. To understand the formation mechanism better and explore possible phase morphology for different blends under HSTWIM, the relationship between the morphology evolution of polymer blends based on polypropylene (PP) under HSTWIM and some intrinsic properties of polymer blends, including viscosity ratio, interfacial tension, and melt elasticity, is systematically investigated in this study. Blends based on PP containing polyethylene (PE), ethylene vinyl alcohol copolymer (EVOH), and polylactic acid (PLA) are used as examples. Compatibilizer has also been added into respective blends to alter their interfacial interaction. It is demonstrated that dispersed phase can be deformed into a layered-like structure if interfacial tension, viscosity ratio, and melt elasticity are relatively small. While some of these values are relatively large, these dispersed droplets are not easily deformed under HSTWIM, forming ellipsoidal or fiber-like structure. The addition of a moderate amount of compatibilizer into these blends is shown to be able to reduce interfacial tension and the size of dispersed phase, thus, allowing more deformation on the dispersed phase. Such a study could provide some guidelines on phase morphology control of immiscible polymer blends under shear during various processing methods.

ORF7 of Varicella-Zoster Virus Is Required for Viral Cytoplasmic Envelopment in Differentiated Neuronal Cells.

Although a varicella-zoster virus (VZV) vaccine has been used for many years, the neuropathy caused by VZV infection is still a major health concern. Open reading frame 7 (ORF7) of VZV has been recognized as a neurotropic gene in vivo, but its neurovirulent role remains unclear. In the present study, we investigated the effect of ORF7 deletion on VZV replication cycle at virus entry, genome replication, gene expression, capsid assembly and cytoplasmic envelopment, and transcellular transmission in differentiated neural progenitor cells (dNPCs) and neuroblastoma SH-SY5Y (dSY5Y) cells. Our results demonstrate that the ORF7 protein is a component of the tegument layer of VZV virions. Deleting ORF7 did not affect viral entry, viral genome replication, or the expression of typical viral genes but clearly impacted cytoplasmic envelopment of VZV capsids, resulting in a dramatic increase of envelope-defective particles and a decrease in intact virions. The defect was more severe in differentiated neuronal cells of dNPCs and dSY5Y. ORF7 deletion also impaired transmission of ORF7-deficient virus among the neuronal cells. These results indicate that ORF7 is required for cytoplasmic envelopment of VZV capsids, virus transmission among neuronal cells, and probably the neuropathy induced by VZV infection.IMPORTANCE The neurological damage caused by varicella-zoster virus (VZV) reactivation is commonly manifested as clinical problems. Thus, identifying viral neurovirulent genes and characterizing their functions are important for relieving VZV related neurological complications. ORF7 has been previously identified as a potential neurotropic gene, but its involvement in VZV replication is unclear. In this study, we found that ORF7 is required for VZV cytoplasmic envelopment in differentiated neuronal cells, and the envelopment deficiency caused by ORF7 deletion results in poor dissemination of VZV among neuronal cells. These findings imply that ORF7 plays a role in neuropathy, highlighting a potential strategy to develop a neurovirulence-attenuated vaccine against chickenpox and herpes zoster and providing a new target for intervention of neuropathy induced by VZV.

Confine Clay in an Alternating Multilayered Structure through Injection Molding: A Simple and Efficient Route to Improve Barrier Performance of Polymeric Materials.

Various methods have been devoted to trigger the formation of multilayered structure for wide range of applications. These methods are often complicated with low production efficiency or require complex equipment. Herein, we demonstrate a simple and efficient method for the fabrication of polymeric sheets containing multilayered structure with enhanced barrier property through high speed thin-wall injection molding (HSIM). To achieve this, montmorillonite (MMT) is added into PE first, then blended with PP to fabricate PE-MMT/PP ternary composites. It is demonstrated that alternating multilayer structure could be obtained in the ternary composites because of low interfacial tension and good viscosity match between different polymer components. MMT is selectively dispersed in PE phase with partial exfoliated/partial intercalated microstructure. 2D-WAXD analysis indicates that the clay tactoids in PE-MMT/PP exhibits an uniplanar-axial orientation with their surface parallel to the molded part surface, while the tactoids in binary PE-MMT composites with the same overall MMT contents illustrate less orientation. The enhanced orientation of nanoclay in PE-MMT/PP could be attributed to the confinement of alternating multilayer structure, which prohibits the tumbling and rotation of nanoplatelets. Therefore, the oxygen barrier property of PE-MMT/PP is superior to that of PE-MMT because of increased gas permeation pathway. Comparing with the results obtained for PE based composites in literature, outstanding barrier property performance (45.7% and 58.2% improvement with 1.5 and 2.5 wt % MMT content, respectively) is achieved in current study. Two issues are considered responsible for such improvement: enhanced MMT orientation caused by the confinement in layered structure, and higher local density of MMT in layered structure induced denser assembly. Finally, enhancement in barrier property by confining impermeable filler into alternating multilayer structure through such simple and efficient method could provide a novel route toward high-performance packaging materials and other functional materials require layered structure.

Fabrication and characterization of waterborne biodegradable polyurethanes 3-dimensional porous scaffolds for vascular tissue engineering.

In this study, a series of 3-D interconnected porous scaffolds with various pore diameters and porosities was fabricated by freeze-drying with non-toxic biodegradable waterborne polyurethane (WBPU) emulsions of different concentration. The structures of these porous scaffolds were characterized by scanning electron microscopy (SEM), and the pore diameters were calculated using CIAS 3.0 software. The pores obtained were 3-D interconnected in the scaffolds. The scaffolds obtained at different pre-freeze temperatures showed a pore diameter ranging from 2.8 to 99.9 microm with a pre-freezing temperature of -60 degrees C and from 13.1 to 229.1 microm with a pre-freezing temperature of -25 degrees C. The scaffolds fabricated with WBPU emulsions of different concentration at the same pre-freezing temperature (-25 degrees C) had pores with mean pore diameter between 90.8 and 39.6 microm and porosity between 92.0 and 80.0%, depending on the emulsion concentration. The effect of porous structure of the scaffolds on adhesion and proliferation of human umbilical vein endothelial cells (HUVECs) cultured in vitro was evaluated using the MTT assay and environmental scanning electron microscopy (ESEM). It was found that the better adhesion and proliferation of HUVECs on 3-D scaffolds of WBPU with relative smaller pore diameter and lower porosity than those on scaffolds with larger pore and higher porosity and film. Our work suggests that fabricating a scaffold with controllable pore diameter and porosity could be a good method to be used in tissue-engineering applications to obtain carriers for cell culture in vitro.

A subchronic intravenous toxicity study of magnesium fructose-1,6-diphosphate in beagle dogs.

Magnesium fructose-1,6-diphosphate is a novel agent of antimyocardial ischaemia. In the present study, the subchronic toxicity of magnesium fructose-1,6-diphosphate was investigated after 13-week repeated intravenous administration in beagle dogs. The animals received doses of 0, 75, 150 and 300 mg/kg/day (three males and three females for each dose). During the study period, clinical signs, mortality, body weights, food consumption, electrocardiogram, urinalysis, haematology, clinical biochemistry, macroscopic findings, organ weights and histopathology were examined. The administration of magnesium fructose-1,6-diphosphate resulted in increased incidence of clinical signs, including salivation and emesis. These effects were transient and were noted in almost all dogs given 300 mg/kg/day and occasionally noted in the 150 mg/kg/day dose-treated animals. Serum magnesium in the 150 mg/kg/day and 300 mg/kg/day dose-treated animals was significantly increased after 6- and 13-week administration, but recovered at the end of a 2-week recovery period. At 6 weeks, a statistically significant decrease in serum electrolytes, including sodium and potassium, was observed in the treatment groups. There were no other treatment-related findings. Under the conditions of the present study, magnesium fructose-1,6-diphosphate did not show any evidence of target organ toxicity. The no-observed-adverse-effect level for 13-week intravenous administration of magnesium fructose-1,6-diphosphate to beagle dogs was considered 75 mg/kg/day based on observations of clinical signs and serum electrolytes.