High performance laser-driven flyers based on a refractory metamaterial perfect absorber.

Laser-driven flyers (LDFs), which can drive metal particles to ultra-high speeds by feeding high-power laser, have been widely used in many fields, such as ignition, space debris simulation, and dynamic high-pressure physics. However, the low energy-utilization efficiency of the ablating layer hinders the development of LDF devices towards low power consumption and miniaturization. Herein, we design and experimentally demonstrate a high-performance LDF based on the refractory metamaterial perfect absorber (RMPA). The RMPA consists by a layer of TiN nano-triangular array, a dielectric layer and a layer of TiN thin film, and is realized by combing the vacuum electron beam deposition and colloid-sphere self-assembled techniques. RMPA can greatly improve the absorptivity of the ablating layer to about 95%, which is comparable to the metal absorbers, but obviously larger than that of the normal Al foil (∼10%). This high-performance RMPA brings a maximum electron temperature of ∼7500 K at ∼0.5 µs and a maximum electron density of ∼1.04 × 1016 cm-3 at ∼1 µs, which are higher than that the LDFs based on normal Al foil and metal absorbers due to the robust structure of RMPA under high-temperature. The final speed of the RMPA-improved LDFs reaches to about 1920 m/s measured by the photonic Doppler velocimetry system, which is about 1.32 times larger than the Ag and Au absorber-improved LDFs, and about 1.74times larger than the normal Al foil LDFs under the same condition. This highest speed unambiguously brings a deepest hole on the Teflon slab surface during the impact experiments. The electromagnetic properties of RMPA, transient speed and accelerated speed, transient electron temperature and density have been systematically investigated in this work.

Deep learning-enabled broadband full-Stokes polarimeter with a portable fiber optical spectrometer.

Portable fiber optical spectrometers (PFOSs) have been widely used in the contemporary industrial and agricultural production and life due its low cost and small volume. PFOSs mainly combine one fiber to guide light and one optical spectrometer to detect spectra. In this work, we demonstrate that PFOSs can work as a broadband full-Stokes polarimeter through slightly bending the fiber several times and establishing the mapping relationship between the Stokes parameters S^ and the bending-dependent light intensities I^, i.e., S^=f(I^). The different bending geometries bring different birefringence effects and reflection effects that change the polarization state of the out-going light. In the meanwhile, the grating owns a polarization-depended diffraction efficiency especially for the asymmetric illumination geometry that introduces an extrinsic chiroptical effect, which is sensitive to both the linear and spin components of light. The minimum mean squared error (MSE) can reach to smaller than 1% for S1, S2, and S3 at 810 nm, and the averaged MSE in the wave band from 440 nm to 840 nm is smaller than 2.5%, where the working wavelength can be easily extended to arbitrary wave band by applying PFOSs with proper parameters. Our findings provide a convenient and practical method for detecting full-Stokes parameters.

Fully continuous spiral phase plate for ultraintense optical vortices.

Ultraintense optical vortices carrying orbital angular momentum have attracted much attention in strong-field laser physics due to their spiral phase and hollow intensity. This Letter introduces a fully continuous spiral phase plate (FC-SPP) that enables the generation of an ultraintense Laguerre-Gaussian beam. An optimization design method based on the spatial filter technique and chirp-z transform is proposed to match the polishing processing and the tightly focusing performance. To enable its use in high-power laser systems, a large-aperture (200 × 200 mm2) FC-SPP has been fabricated on a fused silica substrate through magnetorheological finishing without the use of mask techniques. The far-field phase pattern and intensity distribution based on vector diffraction calculation were compared with those of ideal spiral phase plate and fabricated FC-SPP, which confirmed the high quality of the output vortex beams and their feasibility for producing high-intensity vortices.

miR-1290 promotes IL-8-mediated vascular endothelial cell adhesion by targeting GSK-3ß.

BACKGROUND: MicroRNA-1290 (miR-1290) has been reported to be involved in many diseases and play a key role during the development process. However, the role of miR-1290 in atherosclerosis (AS) is still unclear. METHODS AND RESULTS: The current study showed that the expressions of miR-1290 were high in serum of patients with hyperlipidemia. The functional role of miR-1290 were then investigated in human umbilical vein endothelial cells (HUVECs). Here, we found that miR-1290 expressions were notably enhanced in HUVECs mediated by IL-8. miR-1290 inhibitor repressed monocytic THP-1 cells adhesion to HUVECs by regulating ICAM-1 and VCAM-1, inhibited proliferation through regulating cyclinD1 and PCNA, and inhibited inflammatory response by regulating IL-1ß. Mechanistically, we verified that miR-1290 mimic was able to directly target the 3'-UTR of GSK-3ß mRNA using luciferase reporter assay. Knockdown of GSK-3ß (si-GSK-3ß) promoted HUVECs adhesion and the expression of IL-1ß, and partially restore the depression effect of miR-1290 inhibitor on HUVECs adhesion and inflammation. In contrast, si-GSK-3ß inhibited the proliferation of HUVECs and the expression of cyclinD1 and PCNA. CONCLUSIONS: In summary, our study revealed that miR-1290 promotes IL-8-mediated the adhesion of HUVECs by targeting GSK-3ß. However, GSK-3ß is not the target protein for miR-1290 to regulate the proliferation of HUVECs. Our findings may provide potential target in atherosclerosis treatment.

TMEM98, a novel secretory protein, promotes endothelial cell adhesion as well as vascular smooth muscle cell proliferation and migration.

Transmembrane protein 98 (TMEM98) is a novel gene, and its function has not been well investigated. In a prior study, we have shown that siRNA-mediated knockdown of TMEM98 inhibited interleukin-8 (IL-8) promoted endothelial cell (EC) adhesion, as well as vascular smooth muscle cell (VSMC) proliferation and migration in the vascular endothelial and smooth muscle cell dysfunction. Herein, we used gain- and loss-of-function approaches combined with biochemical techniques to further explore the role of TMEM98 in the vascular wall cell. The expression and secretion of TMEM98 was increased in cultured human umbilical vein endothelial cells (HUVECs) and VSMCs treated with IL-8 and platelet-derived growth factor-BB (PDGF-BB). Also, PDGF-BB secretion was increased in TMEM98-treated HUVECs and VSMCs. Thus, it appears that TMEM98 and PDGF-BB form a positive feedback loop in potentiation of EC adhesion, as well as VSMC proliferation and migration. Knockdown of TMEM98 mediated by siRNA inhibited PDGF-BB-promoted EC adhesion by downregulating the expression of ICAM-1 and VCAM-1, as well as impaired the proliferation and migration of VSMCs by suppressing the AKT/GSK3ß/cyclin D1 signaling pathway and reducing the expression of ß-catenin. Hence, TMEM98 promoted EC adhesion by inducing the expression of ICAM-1/VCAM-1 and triggered VSMC proliferation and migration by activating the ERK and AKT/GSK3ß signaling pathways. Taken together, TMEM98 may serve as a potential therapeutic target for the clinical treatment of vascular endothelial and smooth muscle cell dysfunction.

Asymmetric chiroptical effect from chiral medium filled golden slit grating on substrate.

In this Letter, we report a giant and robust asymmetric chiroptical effect (ACOE) in the chiral medium filled golden slit grating on glass substrate (CMGSG-GS). This ACOE comes from the influence of interface asymmetry on the electromagnetic cross-coupling in the CMGSG-GS, and it is inherently different than that reported in the Faraday medium and the planar anisotropic chiral metamaterials. Both the polarization eigenstate and the transmission matrix are highly dependent on the metal structure used in the CMGSG-GS. The polarization eigenstates of the CMGSG-GS are two co-rotating elliptical states with ellipticity of nearly 0, and they remain mostly unchanged for opposite directions. The transmission matrices of opposite directions are normal matrices, which do not show any symmetric law although the geometry of the CMGSG-GS owns a high rotational symmetry. The reported ACOE gives a measurable physical parameter to reveal the events happening at interface.

Active perfect absorber based on planar anisotropic chiral metamaterials.

Active chiral plasmonics have attracted a considerable amount of research interest for their power to switch the handedness of chiral metamaterials and the potential applications in highly integrated polarization sensitive devices, stereo display fields, and so on. In this work, we propose a kind of active chiral metamaterial absorber (ACMA) composed by planar anisotropic chiral metamaterials (PACMs) and a metal layer. Our in-depth theoretical analysis indicates that the circular conversion dichroism (CCD) from PACMs plays a crucial role to achieve the active chiroptical effect. The CCD effect can enable a differentiated microcavity-interference effect between the left and right circular incident lights and results in a chiroptical effect related to the equivalent optical length between the PACMs and the metal layer. In simulations, a high-performance ACMA, which are composed by the 'Z'-shaped PACMs, is designed, and the maximum reflection CDR from ACMA can reach 0.882. Meanwhile, the minimum reflection CDR can reach to 0, resulting a very large adjustable range of from 0 to 0.882. The maximum modulation sensitivity, which is defined as Mn=∂CDR/∂n and Md=∂CDR/∂d, can reach to about 1368.252 for d=100um and 0.06157 nm-1 for n=4.5,respectively. In addition to the active chiroptical effect, the designed ACMA also shows excellent performance as a sensor, such as when it is being used as a highly-sensitive temperature sensor. In that case, the minimum detected precision can reach approximately 3.067 * 10-8 °C, if VO2 is used to fill the FP cavity.

Optoplasmonic probe to realize scanning near-field Raman microscopy.

Tip-enhanced Raman spectroscopy (TERS) is a powerful scanning probe technique for Raman detections in nanotechnology to date. However, limited by the physical principles of a nanosize tapered metal (or metal-coated) probe used in a TERS device, only far-field without near-field Raman signal can be collected by the TERS with the metal probe. This makes conventional TERS lower in efficiency and cannot be a real near-field Raman microscopy. In this paper, we propose a simple and realizable optoplasmonic probe model, which is composed of a dielectric microsphere and a metal nanobowtie, to realize an ideal scanning near-field Raman microscopy (SNRM). Using finite-difference time-domain (FDTD) method, calculation results of electric field distributions of the proposed probe demonstrate that the probe provides three outstanding characteristics, including strong enhancement of local electric field, nanoscale distributions of the produced electric filed, and collection enhancement of emitted energy with wide wavelength range in near field. These characteristics of the probe resolve the detecting restrictions of metal probes and provide a real near-field scanning method. Therefore, a potentially novel SNRM can be expected to extend Raman application range greatly.

Pure magnetic resonances controlled by the relative azimuth angle between meta-atoms.

A plasmonic molecule showing strong magnetic resonance modes and flexible tunability is proposed. The molecule is composed of two elements, a crescent shaped metallic disk and a smaller one embedded in the cavity of the larger one. The cavity and gap formed by these two elements enable the molecule to support magnetic resonances in the visible and near infrared spectral region, while electric resonances are much weaker to be detected. We show that by changing the relative orientation angle of these two meta-atoms, the resonance wavelength can be changed from the visible to near infrared without modification of the size of the molecule. Anti-crossings and crossings of resonance energy levels, which stem from the coupling effect, are analyzed. When resonating magnetically, the local electric field enhancement at the crescent tip can reach up to hundreds of times with high spatial confinement, which renders the molecule promising applications in many fields.

Diffraction-dependent spin splitting in spin Hall effect of light on reflection.

We report on a diffraction-dependent spin splitting of the paraxial Gaussian light beams on reflection theoretically and experimentally. In the case of horizontal incident polarization, the spin splitting is proportional to the diffraction length of light beams near the Brewster angle. However, the spin splitting is nearly independent with the diffraction length for the vertical incident polarization. By means of the angular spectrum theory, we find that the diffraction-dependent spin splitting is attributed to the first order expansion term of the reflection coefficients with respect to the transverse wave-vector which is closely related to the diffraction length.

Incident-polarization-sensitive and large in-plane-photonic-spin-splitting at the Brewster angle.

In this Letter, we report a phenomenon of large in-plane-photonic-spin-splitting (IPPSS) in the case of a linear polarized Gaussian light beam reflected from an air-glass interface at the Brewster angle. The IPPSS-induced displacement reaches ∼12.4 µm, which is quite larger than the previously reported value. Particularly, the IPPSS is extremely sensitive (∼70 µm/deg) to the incident polarization. We also find that the direction of the spin accumulation can be switched by adjusting the incident polarization slightly. These findings may have useful applications in spin manipulation and precise polarization metrology.

Regulating luminescence thermal quenching based on the synergistic effect of energy transfer and energy gap modulation.

Thermal quenching is the core challenge that hinders the application of luminescent materials. Herein, a synergistic mechanism involving energy transfer and energy gap modulation is proposed based on the local crystal field regulation around sensitizers. The substitution of coordination cation V5+/P5+ weakens the crystal field strength of the sensitizer Bi3+, and the weakening of crystal field splitting causes an increase in the 3P1 energy level, thus increasing its energy gap. Compared with the YVO4:Bi3+,Eu3+ phosphor, the thermal stability of the YV0.25P0.75O4:Bi3+,Eu3+ phosphor is significantly improved, and the relative emission intensity of Eu3+ continuously increases with heating and reaches 1.24 times the original intensity at 523 K and does not show a decreasing trend in the studied temperature range. The anti-thermal quenching performance is mainly attributed to the increasing thermal quenching activation energy (ΔE) of the sensitizer by energy gap modulation, which enhances the energy transfer to compensate thermal quenching. Based on the thermal quenching characteristics of the materials, an optical thermometer is designed. The maximum relative sensitivity (Sr) and absolute sensitivity (Sa) are as high as 1.74% K-1 and 0.59 K-1, respectively, and the minimum temperature resolution reaches 0.288 K. The synergistic effect between energy gap modulation of the sensitizer and energy transfer enables the regulation of thermal quenching. Thus, this study provides a new strategy for exploiting high-performance luminescent materials.

A sharp and selective fluorescence paper-based sensor based on inner filter effect for ratiometric detection of four Sudan dyes in food matrix.

The addition of Sudan dyes with carcinogenic effects to food threatens human health. Herein, a ratiometric fluorescence strip consisting of core-shell upconversion particles (NaYF4:Yb,Tm@NaYF4:Yb,Er), metal-organic frameworks and dual-template molecularly imprinted polymers was developed to selectively and sensitively detect four Sudan dyes based on inner filter effect (detection time only takes 8 min). The high adsorption capacity of metal-organic frameworks and the greater overlap between the emission of NaYF4:Yb,Tm@NaYF4:Yb,Er and the absorbance of four Sudan dyes enable the signal responses to be more sensitive. The limits of detection in chilli powder samples are as low as 29.87 ng/g, 37.55 ng/g, 47.89 ng/g and 51.02 ng/g, with satisfactory recovery (93.32-103.4%) and minor relative standard deviations (≤4.3%). This method broadens the idea for low-cost and portable detection of multiple illegal additives in complex substrates with high selectivity and sensitivity based on one kind of fluorescent strip.

Design and fabrication of three-dimensional chiral nanostructures based on stepwise glancing angle deposition technology.

The chiral structures have displayed some inevitable and fascinating properties in many research fields, such as chemistry, biology, mathematics, and physics. In this Article, we report the use of stepwise glancing angle deposition technology to produce the 3D chiral nanostructures. Through the optimization of deposition parameters (such as the orientation angle of poly styrene spheres (PSs) array, the deposition angle, thickness, and number), a great number of chiral structures have been achieved, and their size depends on the diameter of PS spheres. These chiral structures all can be simulated and predesigned through the use of a 3D geometrical model, which greatly improves the efficiency of this method. In addition, the circular dichroism spectrum shows that these chiral structures own an obvious Cotton effect, indicating their potential application as 3D chiral metamaterials.

Surface-plasmon-polaritons-assisted nanolithography with dual-wavelength illumination for high exposure depth.

We propose a new direct writing nanolithography approach using a plasmonic focusing device and a nano silver mirror with dual-wavelength illumination for high exposure depth. Arrays of pyramid aperture are used to focus the incident light beams into 80 nm light spots. The pyramid combined with a thin silver film coated on the substrate constructs a surface plasmon polaritons (SPP) coupling cavity, which amplifies the intensity of the light field in it by SPP effect and resonance. The transmission depth of the standing wave formed by forward and reflected light could reach hundreds of nanometers. Two lasers with different wavelengths are used as illumination sources to homogenize the light field through complementation between the two standing waves. Simulation results show by using 355 nm and 441 nm wavelengths, a space of 44 nm at the bottom of the photoresist could be obtained after exposure and development. The feature size of resist patterns could be further scaled down, depending on the optimization of parameters of photoresist exposure and development, illumination wavelengths, etc.

MicroRNA-520c-3p suppresses vascular endothelium dysfunction by targeting RELA and regulating the AKT and NF-κB signaling pathways.

Endothelial injury, which can cause endothelial inflammation and dysfunction, is an important mechanism for the development of atherosclerotic plaque. This study aims to investigate the functional role of miR-520c-3p in vascular endothelium during inflammatory diseases such as atherosclerosis. Quantitative real-time PCR was used to detect miR-520c-3p expression in in human umbilical vein endothelial cells (HUVECs) after treatment with platelet-derived growth factor (PDGF). Furthermore, the effects of miR-520c-3p overexpression and silencing on cell proliferation, adhesion, and apoptosis were assessed. Bioinformatics analysis and Biotin-labeled miRNA pull-down assay were used to confirm the targets of miR-520-3p. Then, the effects of miR-520c-3p on AKT and NF-κB signaling pathways were detected by western blot. Herein, we observed that the expression level of miR-520c-3p was downregulated in HUVECs under PDGF stimulation. Overexpression of miR-520c-3p not only decreased cell adhesion but also promoted proliferation and inhibited apoptosis to protect the viability of endothelial cells. It was confirmed that RELA is the target of miR-520c-3p. MiR-520c-3p inhibited the protein phosphorylation of AKT and RELA, and si-RELA reversed the promotion of AKT and RELA protein phosphorylation by anti-miR-520c-3p. In summary, our study suggested that miRNA-520c-3p targeting RELA through AKT and NF-κB signaling pathways regulated the proliferation, apoptosis, and adhesion of vascular endothelial cells. We conclude that miR-520c-3p may play an important role in the suppression of endothelial injury, which could serve as a biomarker and therapeutic target for atherosclerosis.

MicroRNA-520c-3p targeting of RelA/p65 suppresses atherosclerotic plaque formation.

Atherosclerosis is a chronic inflammatory disease, and it's the leading cause of death worldwide. Dysregulation of microRNAs (miRNAs) has been found to be associated with atherosclerosis. miR-520c-3p has been implicated in several types of cancer. However, little is known about the role of miR-520c-3p in atherosclerosis. In this study, we found that miR-520c-3p agomir decreased atherosclerotic plaque size, collagen content, the quantity of PCNA-positive cell and RelA/p65 expression of vascular smooth muscle cells (VSMCs) in the aortic valve of apoE-/- mice in vivo. The possible mechanisms of the protective effects of miR-520c-3p on atherosclerotic mice were then investigated in VSMCs. in vitro experiments showed that miR-520c-3p expressions were significantly reduced in human aortic vascular smooth muscle cell (HASMCs) treated with platelet-derived growth factor (PDGF-BB). miR-520c-3p mimics repress PDGF-BB-mediated the proliferation, migration and decrease in the percentage of cells in G2/M phase, which was associated with downregulation of RelA/p65. Mechanistically, miRNA pull-down, luciferase reporter and mRNA stability assays confirmed miR-520c-3p mimics was able to directly target 3'-UTR of RelA/p65 mRNA and decreased half-life of RelA/p65 mRNA in HASMCs. Overexpression of RelA/p65 reversed the inhibition of cell proliferation induced by miR-520c-3p mimics in HASMCs. In conclusion, our findings suggest that miR-520c-3p inhibits PDGF-BB-mediated the proliferation and migration of HASMCs by targeting RelA/p65, which may provide potential therapeutic strategies in atherosclerosis treatment.

Broadband Asymmetric Light Transmission at Metal/Dielectric Composite Grating.

Optical diode-like effect has sparked growing interest in recent years due to its potential applications in integrated photonic systems. In this paper, we propose and numerically demonstrate a new type of easy-processing metal/dielectric cylinder composite grating on semi-sphere substrate, which can achieve high-contrast asymmetric transmission of unpolarized light for the sum of all diffraction modes in the entire visible region, and effectively guide the diffraction light transmitting out the substrate. The asymmetric light transmission (ALT) ratio is larger than 2 dB in the waveband from 380 nm to 780 nm and the maximum ALT ratio can reach to 13 dB at specified wavelengths. The thorough theoretical research reveals that the proposed metal/dielectric pillar composite grating structure, together with the substrate, can effectively excite localized surface plasmonic resonance (LSPR) effect and waveguide mode (WGM), and enlarge the diffraction difference between forward and backward transmission spaces, including both number of diffraction orders and diffraction efficiency, thus resulting in high-contrast broadband ALT phenomenon. In particular, lowering the symmetry of the grating can achieve polarization-dependent ALT. Such a type of easy-processing ALT device with high performance for both polarized and unpolarized light can be regarded as suitable candidates in practical applications.

Laser-Splashed Three-Dimensional Plasmonic Nanovolcanoes for Steganography in Angular Anisotropy.

Planar optics constructed from subwavelength artificial atoms have been suggested as a route to the physical realization of steganography with controlled intrinsic redundancy at single-pixel levels. Unfortunately, two-dimensional geometries with uniform flat profiles offer limited structural redundancy and make it difficult to create advanced crypto-information in multiplexed physical divisions. Here, we reveal that splashing three-dimensional (3D) plasmonic nanovolcanoes could allow for a steganographic strategy in angular anisotropy, with high resolution, full coloration, and transient control of structural profiles. Highly reproducible 3D morphologies of volcanic nanosplashes are demonstrated by creating a standardized recipe of laser parameters. Such single nanovolcanoes can be well controlled individually at different splashing stages and thus provide a lithography-free fashion to access various spectral responses of angularly coordinated transverse and vertical modes, leading to the full-range coloration. This chip-scale demonstration of steganographic color images in angular anisotropy unfolds a long-ignored scheme for structured metasurfaces and thereby provides a paradigm for information security and anticounterfeiting.

Tuning the Photoluminescence of Graphene Quantum Dots by Photochemical Doping with Nitrogen.

Nitrogen-doped graphene quantum dots (NGQDs) were synthesized by irradiating graphene quantum dots (GQDs) in an NH3 atmosphere. The photoluminescence (PL) properties of the GQDs and the NGQDs samples were investigated. Compared with GQDs, a clear PL blue-shift of NGQDs could be achieved by regulating the irradiating time. The NGQDs obtained by irradiation of GQDs for 70 min had a high N content of 15.34 at % and a PL blue-shift of about 47 nm. This may be due to the fact that photochemical doping of GQDs with nitrogen can significantly enhance the contents of pyridine-like nitrogen, and also effectively decrease the contents of oxygen functional groups of NGQDs, thus leading to the observed obvious PL blue-shift.