Resonant Reflection Research Articles

Voltage-induced modulation of interfacial ionic liquids measured using surface plasmon resonant grating nanostructures.

We have used surface plasmon resonant metal gratings to induce and probe the dielectric response (i.e., electro-optic modulation) of ionic liquids (ILs) at electrode interfaces. Here, the cross-plane electric field at the electrode surface modulates the refractive index of the IL due to the Pockels effect. This is observed as a shift in the resonant angle of the grating (i.e., Δϕ), which can be related to the change in the local index of refraction of the electrolyte (i.e., Δnlocal). The reflection modulation of the IL is compared against a polar (D2O) and a non-polar solvent (benzene) to confirm the electro-optic origin of resonance shift. The electrostatic accumulation of ions from the IL induces local index changes to the gratings over the extent of electrical double layer (EDL) thickness. Finite difference time domain simulations are used to relate the observed shifts in the plasmon resonance and change in reflection to the change in the local index of refraction of the electrolyte and the thickness of the EDL. Simultaneously using the wavelength and intensity shift of the resonance enables us to determine both the effective thickness and Δn of the double layer. We believe that this technique can be used more broadly, allowing the dynamics associated with the potential-induced ordering and rearrangement of ionic species in electrode-solution interfaces.

Dynamic wide gamut color generation using highly lossy metal-based metal-dielectric-metal structure

Dynamic structural color control across a wide spectral range was experimentally achieved via phase retardation between orthogonal polarization states in a Ni/SiO2/Ni-subwavelength grating (SWG) structure. The fabricated Ni/SiO2/Ni-SWG structure exhibited spectrally broadened resonant reflection dips due to the optical damping of Ni. The resonances induced a large phase retardation between the p- and s-polarizations over a wide spectral range, and the retardation changed the reflected polarization states depending on the wavelength. The rotation of the analyzing polarizer enabled the dynamic variation of the reflected structural color from the sample across the wide visible color gamut.

High average power (105 W) Fe:ZnSe laser pumped by radiation of laser diode side-pumped Er:YAG lasers.

A high average power re-frequency operation Fe:ZnSe laser using laser diode side-pumped free-running Er:YAG lasers as activating sources is presented. Two pieces of subsurface layer doped Fe:ZnSe polycrystal are adoptive in a reflective resonator configuration and face-cooled by liquid nitrogen. A maximal Fe:ZnSe laser power of 105 W at a wavelength of 4.1 μm is achieved upon pumping by ten home-made Er:YAG lasers with fiber coupled output working at a frequency of 250 Hz and a pulse duration of ∼420 μs. Corresponding to the maximum Fe:ZnSe laser power, the optical-optical efficiency and slope efficiency with respect to the absorbed pump power are 43% and 44% respectively. The beam quality factor M2 is measured to be 3.4. To the best of our knowledge, it is the highest output average power of an Fe:ZnSe laser reported.

О возможности создания эффективных устройств на поверхностных акустических волнах на частотах выше 6 ГГц

In the paper the interaction of surface acoustic waves (SAWs) with reflectors and interdigital transducers (IDTs) with high aspect ratio electrodes (HAR-electrodes) are investigated. The conditions for the SAW resonant reflection and propagation and the effective IDT conversion of the SAW power into electrical power at the load have been obtained. The real possibility of the effective SAW devices creation (filters, delay lines, resonators, RFID tags) at frequencies above 6 GHz (up to 12-15 GHz) using HAR-electrodes was demonstrated.

Active Acoustic Excitation Method for Leak Detection of Buried Gas Pipelines Based on Cavity Resonance Reflection

Active Acoustic Excitation Method for Leak Detection of Buried Gas Pipelines Based on Cavity Resonance Reflection

Reflective optical fiber SPR sensor with DNA modification for high-sensitive Hg2+ concentration measurement

A reflective optical fiber surface plasmon resonance (SPR) sensor was proposed to measure the concentration of mercury ions (Hg2+). The specific single-stranded DNA was modified on the optical fiber sensing surface coated with Au film by the combination of covalent bond and charge adsorption. The Hg2+ can mismatch with T-T (thymine-thymine) base pairs in single-stranded DNA to form T-Hg2+-T structure, which led to the change of refractive index in sensing area and the wavelength shift of SPR spectrum. The measurement results showed that when the concentration of Hg2+ increased from 0 μM to 13 μM, the resonance spectrum shifted by 14.26 nm. In the linear range between 1–8 μM, the measurement sensitivity of the sensor could reach 1.51 nm/μM. The limit of detection (LOD) was found to be 0.28 μM. Besides, the sensor showed good stability, selectivity and reusability.

Influences of bragg reflection on harbor resonance triggered by irregular wave groups

Gao et al. (2021b) attempted for the first time to use Bragg reflection to mitigate the harbor resonance induced by regular long waves and bi-chromatic short wave groups, revealing its remarkable effectiveness. However, in actual coastal/offshore areas, waves usually exist in the form of irregular wave groups. This article considers the more practical irregular wave groups as the incident waves that excite harbor resonance. The harbor resonance occurring inside an elongated harbor triggered by irregular wave groups and its interactions with Bragg reflection are simulated using a Boussinesq-type model, FUNWAVE 2.0. This article reveals for the first time the capabilities of Bragg resonant reflection to effectively alleviate both the main resonant mode and the whole resonance of the harbor triggered by irregular wave groups. The influences of the geometric parameters of bars (including the bar amplitude and the bar number), the spectral bandwidth parameter of incident irregular wave groups, and the main resonant mode on the following four key parameters are further studied comprehensively: (1) the optimal mitigation effect for the main resonant mode, and (2) its corresponding optimal bar wavelength, (3) the optimal mitigation effect for the whole resonance of the harbor, and (4) its corresponding optimal bar wavelength.

Rational construction of ZnFe2O4 decorated hollow carbon cloth towards effective electromagnetic wave absorption

As typical magnetic materials, ferrites and their composites play dominant roles in the design of high-performance electromagnetic wave (EW) absorber. Solvent thermal method is the most popular route for synthesizing ferrites, while systematical comparison research about the influence of reaction solvents of solvent thermal process on ferrite based material's EW absorption performance has rarely been carried out. Thus in this work, we adopted cotton fabric as raw material, and synthesized two kinds of zinc ferrite decorated hollow carbon cloth (CC@ZnFe2O4) composites through solvent thermal reaction where deionized water and ethylene glycol was adopted as reaction solvents, respectively. After comprehensive and detailed comparison of the structures and performances of these two ferrite composites, the CC@ZnFe2O4 synthesized in deionized water phase possesses an ideal optimal absorption efficiency for EW, that is the minimum reflection loss (RL min) of −46 dB, while the effective absorption bandwidth of CC@ZnFe2O4 composites synthesized in ethylene glycol phase is wider (4.9 GHz). The synergistic effect of impedance matching, interface polarization, magnetic resonance, and multiple reflections co-determined the ideal EW absorption performances of these two samples. The research can not only provide new guidance for the secondary utilization of waste textiles, but also become an important reference for the preparation of ferrite based high-performance EW absorbers through solvent thermal method.

A compact linearly polarized RLSA antenna integrated with circular ring resonator (CRR) for 5G mm-wave applications

This article introduces a compact linearly polarized (LP) radial line slot array antenna (RSLA) that incorporates a metamaterial of circular ring resonator (CRR) reflector for improving the bandwidth. Hence, this enables the antenna to operate at n257 (26.5–29.5), n258(24.25–27.5), and n261(27.5–28.35) frequency bands which are standardized by Federal Communications Commission (FCC) with a minor reduction of the directivity. Due to the short wavelength of the millimeter wave bands, the technique of the RLSA design has been advantageous for achieving high gain. The prototype of the RLSA antenna and the metamaterial CRR reflector are designed and fabricated at 28 GHz resonance frequency utilizing Rogers 5880 substrate and fed using an SSMA coaxial connector with an air gap cavity equivalent to half guide wavelength (λg/2) between substrate and ground plane. The method of integrating the CRR reflector with the LP-RLSA antenna delivered a passband transmission operating at (22–29.5) GHz. The proposed antenna has a similar agreement between simulated and measured for directivity and bandwidth. it achieved a peak directivity of 20 dB with a squinted main lobe at 12° and a fractional bandwidth of 29.13%. The fabricated RLSA antenna dimensions are 130 mm × 130 mm × 10.65 mm which is compact compared to conventional RLSA antennas.

Reflective microring-resonator-based microwave photonic sensor incorporating a self-attention assisted convolutional neural network

In this paper, a reflective microring resonator (MRR)-based microwave photonic (MWP) sensor incorporating a self-attention convolutional neural network (CNN) is presented. An MRR cascaded with an inverse-designed optical reflector is adopted as the sensor probe to allow for utilizing the responses generated from both the clockwise and counterclockwise resonant modes. Through the MWP interrogation, the cascaded resonant modes can be transformed into distinctive deep radio-frequency (RF) spectral notches under different modulator bias conditions. By using a self-attention assisted CNN processing to leverage both the local and global features of the RF spectra, a sensing model with improved accuracy can be established. As a proof of concept, the proposed scheme is experimentally demonstrated in temperature sensing. Even with a small dataset, the root-mean-square error of the sensing model established after training is achieved at 0.026°C, which shows a 10-fold improvement in sensing accuracy compared to that of the traditional linear fitting model.

Electronic and Structural Disorder of the Epitaxial La0.67Sr0.33MnO3 Surface.

Understanding and tuning epitaxial complex oxide films are crucial in controlling the behavior of devices and catalytic processes. Substrate-induced strain, doping, and layer growth are known to influence the electronic and magnetic properties of the bulk of the film. In this study, we demonstrate a clear distinction between the bulk and surface of thin films of La0.67Sr0.33MnO3 in terms of chemical composition, electronic disorder, and surface morphology. We use a combined experimental approach of X-ray-based characterization methods and scanning probe microscopy. Using X-ray diffraction and resonant X-ray reflectivity, we uncover surface nonstoichiometry in the strontium and lanthanum alongside an accumulation of oxygen vacancies. With scanning tunneling microscopy, we observed an electronic phase separation (EPS) on the surface related to this nonstoichiometry. The EPS is likely driving the temperature-dependent resistivity transition and is a cause of proposed mixed-phase ferromagnetic and paramagnetic states near room temperature in these thin films.

Measuring magnetic hysteresis curves with polarized soft X-ray resonant reflectivity.

Calculations and measurements of polarization-dependent soft X-ray scattering intensity are presented during a magnetic hysteresis cycle. It is confirmed that the dependence of the intensity on the magnetic moment can be linear, quadratic or a combination of both, depending on the polarization of the incident X-ray beam and the direction of the magnetic moment. With a linearly polarized beam, the scattered intensity will have a purely quadratic dependence on the magnetic moment when the magnetic moment is parallel to the scattering plane. However, with the magnetic moment perpendicular to the scattering plane, there is also a linear component. This means that, when measuring the hysteresis with linear polarization during a hysteresis cycle, the intensity will be an even function of the applied field when the change in the magnetic moment (and field) is confined within the scattering plane but becomes more complicated when the magnetic moment is out of the scattering plane. Furthermore, with circular polarization, the dependence of the scattered intensity on the moment is a combination of linear and quadratic. With the moment parallel to the scattering plane, the linear component changes with the helicity of the incident beam. Surprisingly, in stark contrast to absorption studies, even when the magnetic moment is perpendicular to the scattering plane there is still a dependence on the moment with a linear component. This linear component is completely independent of the helicity of the beam, meaning that the hysteresis loops will not be inverted with helicity.

Seismic Signature of the Super Cyclone Amphan in Bay of Bengal Using Coastal Observatories Operating Under National Seismological Network of India

AbstractWe examined the seismic noise data collected from coastal and inland observatories in India, affected by the super cyclonic storm Amphan in the Indian Ocean, to understand the storm dynamics. Prominent disturbances in the 0.05–0.50 Hz frequency range were observed at the seismic stations, arising due to ocean‐continent interactions. The coastal stations displayed more pronounced ground motions contrary to the inland stations, with spindle‐shaped seismic wave envelopes intensifying as Amphan approached. The maximum ground displacements and energy occurred hours after the cyclone's eye, with maximum wind speed, moved away from the stations and not when it was close to the station. We observed significant variations in primary (0.05–0.10 Hz) and secondary microseism (0.10–0.50 Hz) energy during Amphan's directional changes. Secondary microseisms in short and long periods were found at 0.20–0.50 Hz and 0.10–0.20 Hz, respectively. Primary microseisms exhibited a simple pattern and were the weakest among the three energy bands. The CAL seismic station's seismic wave envelope showed an en‐echelon feature with increasing amplitude as Amphan approached, indicating the influence of ocean resonance and coastal wave reflection. This study demonstrates monitoring of the tropical cyclone paths based on seismic signatures obtained using microseisms recorded at seismic stations, a cost‐effective tool. Integrating these seismic signals with atmospheric observations in near real‐time would probably enable an effective monitoring of cyclones and timely issuance of their alerts.

Unraveling pH-Dependent Changes in Adsorption Structure of Uranyl on Alumina (012).

Mitigating uranium transport in groundwater is imperative for ensuring access to clean water across the globe. Here, in situ resonant anomalous X-ray reflectivity is used to investigate the adsorption of uranyl on alumina (012) in acidic aqueous solutions, representing typical UVI concentrations of contaminated water near mining sites. The analyses reveal that UVI adsorbs at two distinct heights of 2.4-3.2 and 5-5.3 Å from the surface terminal oxygens. The former is interpreted as the mixture of inner-sphere and outer-sphere complexes that adsorb closest to the surface. The latter is interpreted as an outer-sphere complex that shares one equatorial H2O with the terminal surface oxygen. With increasing pH, we observe an increasing prevalence of these outer-sphere complexes, indicating the enhanced role of the hydrogen bond that stabilizes adsorbed uranyl species. The presented work provides a molecular-scale understanding of sorption of uranyl on Al-based-oxide surfaces that has implications for environmental chemistry and materials science.

Extremely Stable Ag-Based Photonics, Plasmonic, Optical, and Electronic Materials and Devices Designed with Surface Chemistry Engineering for Anti-Tarnish.

Silver (Ag) metal-based structures are promising building blocks for next-generation photonics and electronics owing to their unique characteristics, such as high reflectivity, surface plasmonic resonance effects, high electrical conductivity, and tunable electron transport mechanisms. However, Ag structures exhibit poor sustainability in terms of device performance because harsh chemicals, particularly S2- ions present in the air, can damage their structures, lowering their optical and electrical properties. Here, the surface chemistry of Ag structures with (3-mercaptopropyl)trimethoxysilane (MPTS) ligands at room temperature and under ambient conditions is engineered to prevent deterioration of their optical and electrical properties owing to S2- exposure. Regardless of the dimensions of the Ag structures, the MPTS ligands can be applied to each dimension (0D, 1D, and 3D). Consequently, highly sustainable plasmonic effects (Δλ < 2nm), Fabry-Perot cavity resonance structures (Δλ < 2nm), reflectors (ΔRReflectance < 0.5%), flexible electrodes (ΔRelectrical < 0.1 Ω), and strain gauge sensors (ΔGF < 1), even in S2- exposing conditions is achieved. This strategy is believed to significantly contribute to environmental pollution reduction by decreasing the volume of electronic waste.

Asymmetry of resonant forward/backward reflectivity of metal – multilayer-dielectric nanostructure

Presented in this paper is an experimental and numerical study of direction-dependent asymmetry of resonant optical characteristics inherent to metal – multilayer-dielectric (MMD) nanostructure, which has much in common with the Tamm plasmonic configuration. We demonstrate that when a MMD structure is illuminated from opposite sides, there is a noticeable asymmetry of the forward/backward reflection resonances, contrasting with the strictly symmetrical transmission resonances indicating classical optical reciprocity. Comparative measurements were carried out on a metal film and a quasi-periodic dielectric structure, which are identical to the corresponding parameters of the MMD structure. Directional asymmetry of reflection and transmission is briefly discussed for a modified MMD structure with the Kerr nonlinearity.

OAM-mode coupling by segmented helical-ring-core waveguides inscribed with a femtosecond laser beam.

Azimuthally segmented helical-ring-core waveguides (HRCWs) were fabricated in silica glass by direct laser writing. Triple-segmented waveguides provided single-mode or few-mode light guidance depending on the core diameter. Bragg resonance reflection of the light carrying orbital angular momentum (OAM) was registered confirming the generalized angular phase-matching condition, which considers the azimuthally segmented structure of the waveguides.

Exceptional capture of methane at low pressure by an iron-based metal-organic framework.

The selective capture of methane (CH4) at low concentrations and its separation from N2 are extremely challenging owing to the weak host-guest interactions between CH4 molecules and any sorbent material. Here, we report the exceptional adsorption of CH4 at low pressure and the efficient separation of CH4/N2 by MFM-300(Fe). MFM-300(Fe) shows a very high uptake for CH4 of 0.85 mmol g-1 at 1 mbar and 298 K and a record CH4/N2 selectivity of 45 for porous solids, representing a new benchmark for CH4 capture and CH4/N2 separation. The excellent separation of CH4/N2 by MFM-300(Fe) has been confirmed by dynamic breakthrough experiments. In situ neutron powder diffraction, and solid-state nuclear magnetic resonance and diffuse reflectance infrared Fourier transform spectroscopies, coupled with modelling, reveal a unique and strong binding of CH4 molecules involving Fe-OH⋯CH4 and C⋯phenyl ring interactions within the pores of MFM-300(Fe), thus promoting the exceptional adsorption of CH4 at low pressure.

Graphene‐Based Flexible Optically Transparent Dual‐Tunable Metasurface

AbstractDynamically tunable flexible metasurfaces with optical transparency are essentially useful in stealth, electromagnetic sensing, and camouflage while keeping continuous optical observation and communication. In this paper, a dual‐tunable graphene‐based metasurface is designed based on patterned graphene sandwich structures, showing independent dynamic control of reflection amplitude and resonance frequency, excellent optical transparency, and outstanding flexibility. Both the simulated and measured results demonstrate that the transition from dual band absorption at 12 and 24.8 GHz to broad band absorption from 10 to 25.7 GHz, and the absorption amplitude can be tuned between −5 and −15 dB on average in each case dynamically and independently by applying bias voltage to graphene layers. Lastly, the distributions of the induced electric field and surface currents, as well as an equivalent circuit model, are provided to illustrate the tunable electromagnetic absorption mechanism. The designed metasurface has potential applications that are speculated in the fields of electromagnetic tune and electromagnetic stealth.

Chameleon-inspired supramolecular materials based on cucurbit[7]uril and viologens exhibiting full-color tunable photochromic behavior

Inspired by Chameleons' skin color tuning in response to environmental changes, we design and prepare three inclusion complexes based on the cucurbit[7]uril (Q[7]) host and three viologen guests. Upon light irradiation, the colors of these inclusion complexes in the solid state turn from light colors to vivid three primary colors, i.e., red, green, and blue, respectively. Ultraviolet–visible (UV–vis) diffuse reflectance and electron spin resonance (ESR) spectra reveal that the photochromism can be attributed to the generation of viologen radicals, originating from the photoinduced electron transfer. The results of quantum chemical calculation indicate that Q[7] in the inclusion complexes acts as the electron donor in the photoinduced electron transfer process. Using a color mixing approach and finely manipulating the proportions of the three inclusion complexes, a series of composite photochromic materials (CPMs) can be manufactured, covering a full-color gamut in visible light. On the other hand, due to the ignorable size and shape change of CPMs during the photochromatic processes, the CPMs-based reversible photochromic “printing” and photofading “erase” properties were also used for quick response (QR) code. Therefore, these prominent intelligent features of CPMs open new avenues to explore optical regulated nano-platforms for multiple anti-counterfeiting, biomimetics, and military camouflage applications.