Multifunctional Plasmonic Grating Based on the Phase Modulation of Excitation Light

Multifunctional optical devices are desirable at all times due to their features of flexibility and high efficiency. Based on the principle that the phase of excitation light can be transferred to the generated surface plasmon polaritons (SPPs), a plasmonic grating with three functions is proposed and numerically demonstrated. The Cherenkov SPPs wake or nondiffracting SPPs Bessel beam or focusing SPPs field can be correspondingly excited for the excitation light, which is modulated by a linear gradient phase or a symmetrical phase or a spherical phase, respectively. Moreover, the features of these functions such as the propagation direction of SPPs wake, the size and direction of the SPPs Bessel beam, and the position of SPPs focus can be dynamically manipulated. In consideration of the fact that no extra fabrication is required to obtain the different SPPs fields, the proposed approach can effectively reduce the cost in practical applications.

Development and Validation of a Simple RP-HPLC-PDA Method for Determination of 18 Polyphenols in Grape Juice and Red Wine

According to the trend of a healthy eating awareness trend, having a potential benefit on human health, some polyphenols like flavonoids, resveratrol, hydroxy-stilbenes, and phenolic acids are in the spotlight. Grapes, and one of the most widespread grape product wine; are among the best sources of these polyphenols. In this study, a highly specific, susceptible, and easy chromatographic method was brought out and validated to determine 18 polyphenols in grape and red wines. For this aim, an HPLC-PDA was used, and the separation was accomplished on an RP-ODS4 column. The method comprised of a mobile gradient phase consisting of A solution (acetic acid in water, pH 2.00) and a mixture of the solution A – acetonitrile (20:80, v/v), at a flow rate of 1.0 ml/min, and PDA detection was carried out at 260,280, 320, and 360 nm. According to the results, it can be said that the program indicated good linearity over the range of 1-40 mg L−1 of phenolics with r2>0.99. The recovery of the 18 phenolics ranges from 83.17% to 119.88% at red wines and 88.20% to 117.83% at grape juices. The method is well precise, with the relative standard deviation (RSD) of the average concentration of the phenolic compounds are ranges from 1.22% to 2.02% at red wines and 1.01% to 2.56% at grape juices.

Scattering Analysis and Efficiency Optimization of Dielectric Pancharatnam–Berry-Phase Metasurfaces

In this study, the phase modulation ability of a dielectric Pancharatnam–Berry (PB) phase metasurface, consisting of nanofins, is theoretically analyzed. It is generally considered that the optical thickness of the unit cell of a PB-phase metasurface is λ/2, i.e., a half-waveplate for polarization conversion. It is found that the λ/2 is not essential for achieving a full 2π modulation. Nevertheless, a λ/2 thickness is still needed for a high polarization conversion efficiency. Moreover, a gradient phase metasurface is designed. With the help of the particle swarm optimization (PSO) method, the wavefront errors of the gradient phase metasurface are reduced by fine-tuning the rotation angle of the nanofins. The diffraction efficiency of the gradient phase metasurface is thus improved from 73.4% to 87.3%. This design rule can be utilized to optimize the efficiency of phase-type meta-devices, such as meta-deflectors and metalenses.

Generalized Swift–Hohenberg and phase-field-crystal equations based on a second-gradient phase-field theory

The principle of virtual power is used derive a microforce balance for a second-gradient phase-field theory. In conjunction with constitutive relations consistent with a free-energy imbalance, this balance yields a broad generalization of the Swift–Hohenberg equation. When the phase field is identified with the volume fraction of a conserved constituent, a suitably augmented version of the free-energy imbalance yields constitutive relations which, in conjunction with the microforce balance and the constituent content balance, delivers a broad generalization of the phase-field-crystal equation. Thermodynamically consistent boundary conditions for situations in which the interface between the system and its environment is structureless and cannot support constituent transport are also developed, as are energy decay relations that ensue naturally from the thermodynamic structure of the theory.

Broadband gradient phase discontinuity all-dielectric metasurface

In recent years, metasurfaces have widely been studied due to their ability to offer a spatially varying phase response, low losses, ultrathin size, and easy fabrication. In this paper, a gradient phase discontinuity all-dielectric metasurface consisting of arrays of silicon cube resonator is designed. By adjusting the dimension of the silicon cube resonator, a [Formula: see text] transmission phase covered from [Formula: see text] to [Formula: see text] with [Formula: see text] phase intervals is realized in a frequency from 9.7 GHz to 11.8 GHz. We demonstrate the all-dielectric metasurface can produce the anomalous refraction, vortex beams, and wave-focusing in the microwave and infrared band, respectively. It can be expected that the proposed metasurfaces can find wide applications in communication, designing integrated optical devices, and focusing lenses.

Modeling and Simulation of the Process for the Generation of Gradient Porous Structures From Immiscible Polymer Blends

There has been growing interest in integrating gradient porous structures into synthetic materials like polymers. One particular method for making gradient porous polymers is nonisothermal annealing of co-continuous phase structures of immiscible polymer blends under well-defined thermal boundary conditions. In this paper, we report a method to simulate this nonisothermal phase coarsening process for the generation of gradient-phase structures by the combined implementation of phase-field transport and momentum transport. Specifically, a phase-field equation is solved first to obtain a phase structure with phase size comparable with that of the blend to be annealed. This phase structure is then used as an initial geometry in a two-phase moving-interface flow simulation to gauge into the phase structure coarsening process. Several case studies were performed, and the results show that the controllable generation of gradient-phase structures can be enabled by well-designed geometry and thermal boundary conditions. Using 2D simulations, different types of gradient-phase structures experimentally observed were predicted. With increasing power in computation, the capability of 3D simulation may be unveiled for a more accurate prediction of the nonisothermal phase coarsening process and may ultimately evolve into a useful tool for the design and processing of gradient porous polymers.

Nonreciprocal terahertz beam steering based on magneto-optic metagratings

In this work, an active nonreciprocal THz beam steering has been proposed based on a transversely magnetized metal/InSb metagrating. The nonreciprocal dispersion relation and phase shift characteristics of the metal/InSb waveguide are investigated in details. A metagrating structure with gradient phase shift has been designed based on the metal/InSb waveguide. Under the external magnetic field (EMF), the THz beam can be changed among 0, +1st, and −1st order of the metagrating. Due to the nonreciprocity of the metal/InSb metagrating, the deflection angle can be controlled by changing the positive and negative directions of the EMF, to realize bilateral symmetric scanning from −67.8° to 67.8° with over 70% diffraction efficiency, and this device also exhibits the nonreciprocal one-way transmission as an isolator with the isolation of 13 dB. This low-loss, large deflection degree, nonreciprocal beam scanner has a great potential application in the THz regime.