Recent research and development has been incredibly successful at advancing the capabilities for vacuum electronic device (VED) sources of powerful terahertz (THz) near-THz coherent radiation, both CW or average pulsed. Currently, VED source portfolio covers over 12 orders magnitude in power (mW-to-GW) two frequency (from <; 0.1 to >; 10 THz). Further advances are still possible anticipated. They will be enabled by improved understanding fundamental beam-wave interactions, electromagnetic...

Abstract Coating building envelopes with a passive daytime radiative cooling (PDRC) material has attracted enormous attention as an alternative technique minimal energy consumption and carbon footprint. Despite the exceptional performance scalability of porous polymer coating (PPC), achieving consistent over wide range drying environments remains major challenge for its commercialization paint. Herein, we demonstrate humidity vulnerability PPC during process propose simple strategy to...

We report an effective method to enhance and modify the magnetic plasmon (MP) resonance in three-dimensional (3D) optical metamaterials consisting of periodic arrays silver vertical split-ring resonators (VSRRs) for high-sensitivity sensing. By positioning 3D above a thick film separated by silica dielectric spacer layer, strong coupling between MP VSRRs surface plasmons polaritons (SPPs) propagating on can be realized gives rise ultra-narrowband hybrid mode with huge enhancement fields. For...

The authors show that evanescent tunneling transmission of effective surface plasmon polaritons between two counterstreaming electron beams noticeably increases Smith-Purcell radiation (SPR) intensity by about orders magnitude as well lower its transition threshold from a spontaneous emission to stimulated one. An mechanism the superradiant SPR is theoretically analyzed dielectric conversion structured metal and boundary matching condition Maxwell’s equations in comparison with numerical simulations.

It is well known that a suspended monolayer graphene has weak light absorption efficiency of about 2.3% at normal incidence, which disadvantageous to some applications in optoelectronic devices. In this work, we will numerically study multiband and broadband enhancement over the whole visible spectrum, due multiple magnetic dipole resonances metamaterials. The unit cell metamaterials composed sandwiched between four Ag nanodisks with different diameters SiO2 spacer on an substrate....

We report an effective strategy to enhance the localized surface plasmon resonances (LSPRs) of metallic nanoparticles by introducing a Fabry-Pérot (FP) cavity for high-quality sensing. The concept is based on combined excitation LSPRs in and optical modes supported FP cavities, whose strong interactions result two ultra-narrowband hybridized with huge electric field enhancement. A double-band plasmonic nanosensor, refractive index sensitivity approaching 600 nm/RIU figure merit exceeding 28...

We present an ab initio molecular dynamics study of the alkali metal ions Li+, Na+, K+ and Cs+, alkaline earth Mg2+ Ca2+ in both pure water electrolyte solutions containing counterions Cl- SO42-. Simulations were conducted using different density functional theory methods (PBE, BLYP revPBE), with without inclusion dispersion interactions (-D3). Analysis ion-water structure interaction strength, exchange between first second hydration shell, hydrogen bond network low-frequency reorientation...

Abstract Flexible and rechargeable Zn–air batteries (ZAB) are promising candidates for attaining the high energy density required next‐generation storage devices given their half‐open cathode configuration. However, poor interfacial contact between immobilized solid‐state electrolyte porous cathode, drying‐out of water in at low relative humidity (RH) 30% or less, cause performance short lifespan. Herein, a novel hygroscopic dough‐type with water‐absorbing malleable free‐standing...

This paper presents a study of coherent and superradiant Smith-Purcell (SP) radiation with the help two-dimensional particle-in-cell (PIC) simulation. The simulation model supposes rectangular grating period length $173\text{ }\ensuremath{\mu}\mathrm{m}$ to be driven by single electron bunch, train periodic bunches continuous beam, respectively. We chose 40 keV as initial energy electrons therefore SP frequency falls in THz regime. From our bunch we distinguish true separated time from...

The circuits for millimeter wave vacuum electron devices with all circuit elements including an beam tunnel are microfabricated by two-step deep-etch x-ray lithography (x-ray LIGA). discrepancies of eigenfrequency between experiment and simulation within 1.1% in a coupled-cavity structure 1.4% folded waveguide when the operating frequency is about 100GHz. Furthermore, measured tolerance below 2μm, surface roughness 20–70nm, LIGA-fabricated implies LIGA microfabrication has potential...

We introduce the subwavelength transmission of an effective surface plasmon beyond light zone via proximity interaction convection electrons with a metal grating. A comparative analysis dielectric homogenization and finite-difference-time-domain simulation shows that out-of-phase-like modes (pi modes) have strong below cutoff frequency relying on parametric condition structural dimension electronic energy. The synchronous spatial field charge distribution pi mode system confirms evanescent...

Terahertz (THz) technology has emerged for biomedical applications such as scanning, molecular spectroscopy and medical imaging. Although a thorough assessment to predict potential concerns precede before practical utilization of THz source, the biological effect radiation is not yet fully understood with scant related investigations. Here, we applied femtosecond-terahertz (fs-THz) pulse mouse skin evaluate non-thermal effects radiation. Analysis genome-wide expression profile in...

We study theoretically the interaction effects between optical waveguide modes and magnetic resonances in metamaterials, consisting of periodic arrays paired metallic nanodisks lying on a dielectric substrate. The plasmon near-field coupling individual nanodisk pairs results into resonances. arrangement can excite propagating adjacent waveguide. When are close to by varying array period, they interact form two hybridized modes. A model oscillators is also proposed predict well positions In...

We first investigate numerically photonic microcavity-enhanced magnetic plasmon (MP) resonance in metamaterials for high-quality refractive index sensing. The consist of a top periodic array U-shaped metallic split-ring resonators (SRRs), middle dielectric layer, and bottom backed plate. SRRs that are placed at about Bragg distance above the plate constitute microcavity. Because MP excited is coupled to microcavity mode supported by microcavity, radiative damping strongly reduced,...

Fingerprints are unique to primates and koalas but what advantages do these features of our hands feet provide us compared with the smooth pads carnivorans, e.g., feline or ursine species? It has been argued that epidermal ridges on finger decrease friction when in contact surfaces, promote interlocking rough channel excess water, prevent blistering, enhance tactile sensitivity. Here, we found they were at origin a moisture-regulating mechanism, which ensures an optimal hydration keratin...

High-power microwave sources applied to a directed-energy weapon can lead permanent damage by radiating concentrated energy in specific direction disturb or overload electronic equipment. The effect analysis on the target, such as electronics exposed electromagnetic pulse, should be considered an important factor determining performance of high-power and conducting experimental evaluations. In this study, magnetically insulated transmission line oscillator, one representative based vacuum...

The electromagnetic response of a metallic metamaterial to fast-moving electrons is studied by numerical simulations. considered one-dimensional array slits perforated on film and found generate Cerenkov wakes when the electron beam travels near its surface. There no energy threshold for generation such wakes, which would be promising lower operation in compact free-electron-lasers. Moreover, analyzing spectral dependence light, it possible map dispersion relation guided modes supported metamaterial.

Abstract We present an atomistic simulation scheme for the determination of hydration number ( h ) aqueous electrolyte solutions based on calculation water dipole reorientation dynamics. In this methodology, time evolution solution generated from ab initio molecular dynamics simulations is used to compute different subpopulations. The value determined by considering whether subpopulations retarded with respect bulk‐like behavior. application computational protocol magnesium chloride (MgCl 2...

A simulation of coherent and super-radiant Smith-Purcell radiation is performed in the gigahertz regime using a three-dimensional particle-in-cell code. The model supposes rectangular grating to be driven by single electron bunch train periodic bunches, respectively. true distinguished from evanescent wave, which has an angle independent frequency lower than minimum allowed frequency. We also find that radiations excited bunches are emitted at higher harmonics bunching corresponding angles.

We report experimental and finite-difference time-domain simulation studies on terahertz (THz) characteristics of band gaps by using metal grooves which are located inside the flare parallel-plate waveguide. The vertically localized standing-wave cavity mode (SWCM) between upper waveguide surface groove bottom, horizontally SWCM two side walls (groove cavity) observed. E field intensity in is very strongly enchanced three order higher than that input THz. 4 except Bragg gap caused π radian...

We investigate the influence of 1, 2-ditetradecanoyl-sn-glycero-3-phosphocholine lipid bilayer phases on water reorientation dynamics with terahertz time domain spectroscopy. The phase lipids was controlled by temperature in range 14–35 °C. During gel-to-fluid transition, hydration ratio drastically changed from 0.3 to 0.6. absorption coefficient increased gel and then decreased fluid phase. dielectric relaxation solution initially but after transition. This indicates that are restricted...

A folded waveguide (FW) is a promising slow-wave structure (SWS) for millimeter-wave traveling-wave tubes (TWTs) with the advantages of high power and considerable bandwidth. novel rectangular groove-loaded FW SWS analyzed purpose gaining higher smaller size compared normal circuit. The high-frequency characteristics, including dispersion properties interaction impedance, are investigated by numerical simulation, nonlinear large-signal performance such TWT also 3-D particle-in-cell code...

Radiofrequency (RF) radiation does not transfer high energy to break the covalent bonds of macromolecules, but these low stimuli might be sufficient induce molecular responses in a specific manner. We monitored effect 1,763 MHz RF on cultured human dermal papilla cells (hDPCs) by evaluating changes expression cytokines related hair growth. The insulin-like growth factor-1 (IGF-1) mRNA hDPCs was significantly induced upon at absorption rate 10 W/kg, which resulted increased B-cell chronic...

We investigated the foundations for high-frequency vacuum electron devices experimentally, with emphasis on deep etch X-ray lithography: lithographie, galvanoformung, abformung (LIGA) to fabricate a miniaturized interaction circuit and photonic crystal (PC) resonator excite stable high-order mode. The successful operation of LIGA-fabricated folded-waveguide traveling-wave tube was reported. From such physical considerations as Debye length band gap, we proposed reflex klystron adopting cold...