Merging diverse bound states in the continuum: from intrinsic to extrinsic scenarios.

Bound states in the continuum (BICs) in photonic crystal slabs are characterized as vortex centers in far-field polarization and infinite quality (Q) factors, which can be dynamically manipulated in momentum space to construct the singularity configurations with functionalities such as merging BICs for further suppress scattering loss of nearby resonance. However, the vast majority of research focuses on two types of intrinsic BICs for simplicity, because these polarization singularities affect each other, and are even prone to annihilation. Here, we introduce the extrinsic (Fabry-Pérot) BICs and combine them with the intrinsic BICs to merge diverse BICs in momentum space. The extrinsic BICs can move independently of the intrinsic BICs, providing an unprecedented degree of freedom to reduce the complexity of constructing merging BIC configurations. Interestingly, an interaction of oppositely charged BICs that is collision beyond annihilation is revealed, which only exchanges the topological charge of BICs but not affect their existence. Following the proposed strategy, four-types-BICs merging and steerable three-types merging are achieved at the Γ and off-Γ points, further boosting the Q factor scaling rule up to Q∝k x-14 and Q∝k x-6 respectively. Our findings suggest a systematic route to arrange abundant BICs, may facilitate some applications including beam steering, optical trapping and enhancing the light-matter interactions.

Ultrahigh-Q and angle-robust chiroptical resonances beyond BIC splitting.

Chiroptical resonances inspired by bound states in the continuum (BICs) open a new, to the best of our knowledge, avenue to enhance chiral light-matter interaction. Symmetry breaking is the widely employed way, wherein the circularly polarized states (CPSs) arise from BIC splitting. Here, we utilize a far-field interference mechanism to create ultrahigh-Q (typically, 2.36 × 106) chiroptical resonance beyond BIC splitting, in which CPSs coexist with BICs in the momentum space. Accordingly, the spin-selective absorption with ultranarrow linewidth is achieved at the CPS points, which can be regulated by monolayer transition metal dichalcogenides (TMDCs). In addition, the chiral response of our scheme exhibits the incident-direction robustness and flexible tunability. Our findings may facilitate potential applications in light manipulation, spin-valley interaction, and chiral sensing.

Two-dimensional spatial coherence measurement of X-ray sources using aperture array mask.

Fourth-generation synchrotron radiation delivers x-ray sources with unprecedented coherence and brilliance, which enables the development of many advanced coherent techniques taking advantage of the inherent high coherence of the x-ray beams. Simple and accurate measurement of two-dimensional (2D) coherence is of utmost importance for the applications of these coherent experimental techniques. Here, we propose a novel approach based on diffraction of aperture array mask (AAM) to obtain accurate 2D spatial coherence with a single-shot measurement. We utilize a coherent mode decomposition algorithm to simulate the diffraction of AAM illuminated by Gaussian-Schell model beam and demonstrate that spatial coherence function of the incident light beam can be accurately and robustly retrieved. We expect that this new approach will be applied into transverse coherence measurements for the new-generation synchrotron radiation source and relevant coherent experimental techniques.

Pure longitudinal reversible magnetization at the focal spot generated by a bifunctional triplex metalens.

Bifunctional metalens for generation of pure longitudinal magnetization focal spot with reversible magnetization direction is greatly desired for the miniaturization and integration of all-optical magnetic storage. In this paper, we demonstrate a bifunctional triplex metalens that integrates the functions of an azimuthal polarizer, a helical phase plate, and a focusing lens for all-optical magnetic storage. Constructing the triplex metalens with tetratomic macropixels, the direction of the longitudinal magnetization at the focal spot can be flexibly switched by reversing the handedness of the incident light. Nearly perfect circularly polarized focal spot for left-handed or right-handed incident polarization are experimentally demonstrated, which is well consistent with the numerical simulations. The proposed bifunctional triplex metalens paves the way for the application of metalens in all-optical magnetic storage.

Monitoring the evaporation of a sessile water droplet with a chromatic confocal measurement system.

In this Letter, a chromatic confocal measurement system with high stability and accuracy is presented to monitor the evaporation of a sessile water droplet. The stability and accuracy of the system are tested by measuring the thickness of a cover glass. To compensate for the measurement error caused by the lensing effect of the sessile water droplet, a spherical cap model is proposed. Together with the parallel plate model, the contact angle of the water droplet can also be obtained. The evaporation process of sessile water droplet under different environment is monitored experimentally in this work, which demonstrates the potential application of chromatic confocal measurement system in the field of experimental fluid dynamics.

Resolving the subwavelength width of nanoslits by full-Stokes polarization analysis of scattered light.

Due to the diffraction limit, subwavelength nanoslits (whose width is strictly smaller than λ/2) are hard to resolve by optical microscopy. Here, we overcome the diffraction limit by measuring the full Stokes parameters of the scattered field of the subwavelength nanoslits with varying width under the illumination of a linearly-polarized laser with a 45° polarization orientation angle. Because of the depolarization effect arising from the different phase delay and amplitude transmittance for TM polarization (perpendicular to the long axis of slit) and TE polarization (parallel to the long axis of slit), the state of polarization (SOP) of the scattered light strongly depends on the slit width for subwavelength nanoslits. After correcting for residual background light, the nanoslit width measured by the SOP of scattered light is consistent with the scanning electron microscopy (SEM) measurement. The simulation and experiment in this work demonstrate a new far-field optical technique to determine the width of subwavelength nanoslits by studying the SOP of the scattered light.

Gab1 Overexpression Attenuates Susceptibility to Ventricular Arrhythmias in Pressure Overloaded Heart Failure Mouse Hearts.

PURPOSE: Grb2 associated binding protein 1 (Gab1) is an adaptor protein that is important for intracellular signal transduction which involved in several pathological process. However, the role of Gab1 in pressure overload-induced ventricular arrhythmias (VAs) remain poorly understood. In the current study, we aimed to test the role of Gab1 in VA susceptibility induced by pressure overload. METHODS: We overexpressed Gab1 in the hearts using an adeno-associated virus 9 (AAV9) system through tail vein injection. Aortic banding (AB) surgery was performed in C57BL6/J mice to induce heart failure (HF). Four weeks following AB, histology, echocardiography, and biochemical analysis were conducted to investigate cardiac structural remodeling and electrophysiological studies were performed to check the electrical remodeling. Western blot analysis was used to explore the underlying mechanisms. RESULTS: The mRNA and protein expression were downregulated in AB hearts compared to sham hearts. Gab1 overexpression significantly reversed AB-induced cardiac structural remodeling including ameliorated AB-induced cardiac dysfunction, cardiac fibrosis, and inflammatory response. Moreover, Gab1 overexpression also markedly alleviated AB-induced electrical remodeling including ion channel alterations and VA susceptibility. Mechanistically, we found that TLR4/MyD88/NF-κB contributes to the cardio protective effect of Gab1 overexpression on AB-induced VAs. CONCLUSIONS: Our study manifested that Gab1 may serve as a promising anti-arrhythmic target via inhibiting TLR4/MyD88/NF-κB signaling pathway induced by AB.

Generation of pure longitudinal magnetization focal spot with a triplex metalens.

A pure longitudinal magnetization focal spot is greatly desired by all-optical magnetic recording. In this Letter, a triplex metalens is proposed and demonstrated to possess triple functions of an azimuthal polarization converter, a helical phase plate, and a focusing lens. The three-in-one combination enables conversion of linearly polarized incident light to the first-order azimuthally polarized vortex beam and focusing into a diffraction-limited spot. The state of polarization of the focal spot is measured to be pure circular polarization implying that a pure longitudinal magnetization field can be induced by the inverse Faraday effect. The lateral full width at half-maximum of the focal spot is 1.9 µm, and the experimental conversion efficiency of the metasurface is about 19.3%.

Optical anisotropy of self-organized gold quasi-blazed nanostructures based on a broad ion beam.

To circumvent elaborate conventional lithographic methods for realizing metallic nanostructures, it is necessary to develop self-organized nanofabrication methods for suitable template structures and their optical characterization. We demonstrate the potential of ion bombardment with impurity co-deposition to fabricate terraced or quasi-blazed nanostructure templates. Self-organized terraced nanostructures on fused silica were fabricated using Ar+ ion bombardment with iron impurity co-deposition and subsequent Au shadow deposition. The aspect ratios are enhanced threefold, and the range of nanostructure period variation is significantly increased with respect to that of conventional nanostructures realized by pure ion bombardment. We reveal the key features of the method via atomic force microscopy and optical characterization. Variable-profile quasiperiodic nanostructures with periods of 100-450 nm, heights of 25-180 nm, and blaze angles of 10°-25° were fabricated over an area of 20×40mm2, and these exhibited tunable and broadening optical anisotropy across the nanostructured area. Thus, the proposed method is a viable technique for rapid, cost-effective, and deterministic fabrication of variable nanostructure templates for potential optical applications.

Asymmetric Excitation of Surface Plasmon Polaritons via Paired Slot Antennas for Angstrom Displacement Sensing.

Optical antennas enable efficient coupling between propagating light and bonding electromagnetic waves like surface plasmon polaritons (SPPs). Under the illumination of inhomogeneous optical fields, propagating SPPs mediated by multimode antennas could be spatially asymmetric and the asymmetry strongly depends on the position of the antennas relative to the illumination field. Here we develop such asymmetric excitation of SPPs through illuminating a pair of slot antennas with the (1,0) mode Hermite-Gaussian beam. The physical scenario of the interaction between the illumination optical field and the paired slot antennas are elaborated by full-wave electromagnetic simulations. We also carry out experiments to monitor the asymmetric SPPs propagation with a back-focal plane imaging technique. By retrieving the asymmetric intensity ratio of the SPP pattern in the back-focal plane image, lateral displacement of the antennas down to angstrom level is demonstrated.

Strong longitudinal coupling of Tamm plasmon polaritons in graphene/DBR/Ag hybrid structure.

In this paper, strong longitudinal coupling of the Tamm plasmon polaritons (TPPs) is investigated in a graphene/DBR/Ag slab hybrid system. It is found that TPPs can be excited at both the top graphene and the bottom silver slab interface, which can strongly interact with each other in this coupled structure. Numerical simulation results demonstrate that the vertical Tamm plasmon coupling can be either tuned by adjusting the geometric parameters or actively controlled by the Fermi energy in graphene sheet as well as the incident angle of light, allowing for strong light-matter interaction with a tunable dual-band perfect absorption. Moreover, the coupling strength of the hybrid modes exhibits a large tuning range, from a large Rabi splitting to an extremely narrow induced transparency in this coupled regime. Coupled mode theory has been employed to explain the strong coupling phenomenon. The controllable TPP coupling with an ultrahigh dual-band absorption capability offered by this simple layered structure opens new avenues for developing a broad range of graphene-based active optoelectronic and polaritonic devices.

Nanoscale displacement sensing based on the interaction of a Gaussian beam with dielectric nano-dimer antennas.

Measuring nanoscale displacement is crucial for optical nanometrology and optical calibration. Here, we present a comprehensive analysis of the far-field scattering of dielectric nano-dimer antennas excited precisely by a Gaussian beam. We demonstrated that the interaction of a Gaussian beam with a dielectric nanoantenna will lead to remarkable sensitivity of the far-field scattering to the displacement at a scale much smaller than the wavelength. The electric/magnetic dipole-dipole interaction model is drawn to analyze the far-field scattering and the results are in good agreement with numerical simulations. This study will pave a simple way to a novel position detection and displacement sensing based on the interaction of general Gaussian beam with nanoantennas.

Fluorescence emission difference with surface plasmon-coupled emission applied in confocal microscopy.

We combined confocal surface plasmon coupled emission microscopy (C-SPCEM) together with fluorescence emission difference (FED) technique to pursuit super-resolution fluorescent image. Solid or hollow point spread function (PSF) for C-SPCEM is achieved with radially-polarized or circularly-polarized illumination. The reason why PSF can be manipulated by the polarization of illumination light is corroborated by the interaction of fluorescent emitter with vector focal field on the plasmonic substrate. After introduction of FED technique, PSF for C-SPECM can shrunk to around λ/4 in full-width half-maximum, which is unambiguously beyond Rayleigh's diffraction limit. The super-resolution capability of C-SPCEM with FED technique is experimentally demonstrated by imaging aggregated fluorescent beads with 150 nm in diameter.

Optical field manipulation by dual magnetic resonances of a silicon metasurface.

In this Letter, we study the influence of magnetic mode dispersion on the performance of a metasurface cylindrical vector beam (CVB) generator. An optical field after a metasurface CVB generator can be manipulated by polarization-dependent transmittance arising from dual magnetic resonance of silicon nanopillars. A perfect CVB is only generated when the transmittances are equal for two orthogonal polarization. Two magnetic resonant wavelengths can be spatially separated because of the coherent superposition between the residual incident light and the generating CVB, which is potentially useful for a compact multiplex color router.

Effects of Chronic Intractable Insomnia on Inflammatory Cytokines, Blood Pressure Characteristics, and Antihypertensive Efficacy in Hypertensive Patients.

BACKGROUND This study investigated the changes in blood pressure and inflammatory cytokines in patients with chronic intractable insomnia, and explored the effects of chronic intractable insomnia on antihypertensive efficacy. MATERIAL AND METHODS A total of 248 patients with hypertension admitted to our hospital from 2008 to 2017 were enrolled. We enrolled 124 patients without chronic insomnia in the control group, while 124 patients with chronic insomnia were included in the treatment group. The treatment group received estazolam and was further subdivided into the effective group (n=96) and the ineffective group (n=28) according to Sleep Dysfunction Rating Scale (SDRS) scores. Sleep quality before and after treatment was determined. RESULTS Antihypertensive treatment with eplerenone (50 mg) significantly reduced SDRS scores, C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), matrix metalloproteinase-9 (MMP-9), serum intercellular adhesion molecules (sICAM), and IL-1ß levels, as well as systolic blood pressures (SBP) and diastolic blood pressures (DBP), with elevation of non-dipper blood pressure rhythm (P<0.05). The inhibition of intractable insomnia significantly downregulated SBP and DBP, as well as serum inflammatory cytokines such as CRP and TNF-α, showing a favorable effect on antihypertensive function. CONCLUSIONS Alleviation of chronic intractable insomnia facilitates hypertension therapy through decreasing levels of inflammatory cytokines and the proportion of non-dipper blood pressure rhythm, which offers insights for the treatment of hypertension.

Free-standing Ag triangle arrays a configurable vertical gap for surface enhanced Raman spectroscopy.

Large-area ordered arrays with dense hotspots are highly desirable substrates for surface enhanced Raman scattering (SERS). In this paper, we present a quasi-3D SERS substrate of free-standing Ag triangle arrays (FATA) which was fabricated by nanosphere lithography incorporated with photolithography and Ag covering. A significant SERS effect arises from a strongly enhanced local electric field within the tiny gaps between the suspended Ag triangle and the Ag baseplate. The SERS intensity relative standard deviation is less than 7.6%, leading to excellent reliability for Raman detection. The simple fabrication of the Ag film covering FATA nanostructures provides a practical solution for large-area, highly efficient and reproducible SERS substrates.

Unidirectional reflectionless phenomenon in periodic ternary layered material.

Unidirectional reflectionless phenomenon is reported in periodic ternary layered material (PTLM). The unit of the material is composed of two real dielectric layers and a complex medium (loss or gain) layer. The model is analyzed by coupled mode theory. Because of the asymmetric coupling between the forward and backward propagating modes, the left- and right-side reflectivities of this PTLM are generally unequal. The necessary and sufficient (NS) condition for unidirectional reflectionless phenomenon is presented in a concise formulation. And the underlying physical mechanism of the unidirectional reflectionless phenomenon in this material is revealed by numerical simulations. Both unidirectional reflectionless and symmetric reflection phenomena can be realized by judicious choice of the structural and optical parameters.

Raman scattering enhanced within the plasmonic gap between an isolated Ag triangular nanoplate and Ag film.

Enhanced electromagnetic field in the tiny gaps between metallic nanostructures holds great promise in optical applications. Herein, we report novel out-of-plane nanogaps composed of micrometer-sized Ag triangular nanoplates (AgTN) on Ag films. Notably, the new coupled plasmonic structure can dramatically enhance the surface-enhanced Raman scattering (SERS) by visible laser excitation, although the micrometer-sized AgTN has localized plasmon resonance at infrared wavelength. This enhancement is derived from the gap plasmon polariton between the AgTN and Ag film, which is excited via the antenna effect of the corner and edge of the AgTN. Systematic SERS studies indicated that the plasmon enhancement was on the order of corner > edge > face. These results were further verified by theoretical simulations. Our device paves the way for rational design of sensitive SERS substrates by judiciously choosing appropriate nanoparticles and optimizing the gap distance.

Large-area, reproducible and sensitive plasmonic MIM substrates for surface-enhanced Raman scattering.

Vertically coupled plasmonic structure is of great interest for surface-enhanced Raman scattering (SERS). In this paper, a large-area reproducible SERS substrate is fabricated and demonstrated by a vertically coupled structure composed of Ag triangle arrays on Ag films separated by a nanometric dielectric layer. This metal-insulator-metal (MIM) nanostructure has broadband resonance covering both the laser excitation and Stokes frequencies. Thanks to the convenience of controlling the gap distance by thin dielectric film, the SERS substrate is optimized to yield the best enhancement. The SERS enhancement factor is estimated to be 5.8 × 106 for on-resonant pumping with a 532 nm laser. The uniformity and reproducibility of the SERS substrate are also demonstrated. Our results pave the way for rational design of sensitive SERS substrates and harmless exciting SERS signals.

Near-field coupling and resonant cavity modes in plasmonic nanorod metamaterials.

Plasmonic resonant cavities are capable of confining light at the nanoscale, resulting in both enhanced local electromagnetic fields and lower mode volumes. However, conventional plasmonic resonant cavities possess large Ohmic losses at metal-dielectric interfaces. Plasmonic near-field coupling plays a key role in a design of photonic components based on the resonant cavities because of the possibility to reduce losses. Here, we study the plasmonic near-field coupling in the silver nanorod metamaterials treated as resonant nanostructured optical cavities. Reflectance measurements reveal the existence of multiple resonance modes of the nanorod metamaterials, which is consistent with our theoretical analysis. Furthermore, our numerical simulations show that the electric field at the longitudinal resonances forms standing waves in the nanocavities due to the near-field coupling between the adjacent nanorods, and a new hybrid mode emerges due to a coupling between nanorods and a gold-film substrate. We demonstrate that this coupling can be controlled by changing the gap between the silver nanorod array and gold substrate.