Resonant Reflection Research Articles

Metasurface Source Antenna Gain Improvement Using Simple Side Metal Structure.

As metasurfaces are in the spotlight, research is being conducted to incorporate them into transmitarray (TA) antennas. Among these, as an attempt to create a low-profile design, a patch antenna classified as low-gain can be utilized as an appropriate source antenna. However, for high efficiency of the TA, the gain of the source antenna must be fundamentally improved. For this, a simple side metal structure was applied to a metallic cross-type slot transmitarray. This acts as a resonant element and reflector by utilizing the electromagnetic wave radiated from the source antenna. The changes in the center frequency and gain due to the application of the side metal structure to the source antenna were analyzed. The gain of the source antenna was improved by a total of 4.63 dB. This is expected to be applied to create various source waves and to conduct future research on improving the gain in transmitarray antennas.

A novel circularly polarized antenna array methodology for early identification of kidney tumors

Kidney cancer is a significant health concern worldwide, with early detection crucial for successful treatment outcomes. Recently, there has been an increasing focus on investigating affordable and non-intrusive methods for detecting cancer at its early stages. This proposed approach delves into the utilization of antenna arrays to identify kidney cancer. Specifically, antenna array with circular polarization has been crafted to identify tumors in the human kidney. This array design has been implemented using CST software, operating at 2.4 GHz. The antenna array having a dimension of 150 mm x 150 mm. The array consists of four-square patches each having a length of 30 mm and the spacing between the patches is preferred to be 20 mm for ensuring the mutual coupling. FR4 substrate is used with the relative permittivity 4.3 and 1.6 mm thickness. The axial ratio of the circularly polarized antenna is 0.9 dB at 2.4 GHz. The reflection coefficient S 11 = –30dB. The renal phantom in humans has been built with the kidney, adrenal gland, ureter, skin, fat, and muscle components to allow for precise simulation. Following that, four stages of cancer tumors were built employing all of the necessary qualities. For every stage of the cancer tumor, the reflection coefficient growth and resonance frequency shift are calculated. For the initial stages, the resonance frequency shift is very low. Consequently, the primary determinant of detection is the rise in S 11 . For 3rd and 4th stages of the tumor, there is a significant change in resonance frequency and increase S 11 , which facilitates identification. The calculated specific absorption rate (SAR) is a smaller amount than the safety thresholds, indicating that using this method is safe. Overall, this research points to a novel, easy-to-use method for kidney cancer screening. This method has the following benefits: it is non-invasive, safe, quick, affordable, and comfortable, and it emits no ionizing radiation during the measurement process. Furthermore, a range of output parameters such as gain, directivity, and polar radiation have been accurately computed.

Vectorial spatial differentiation of optical beams with metal–dielectric multilayers enabled by spin Hall effect of light and resonant reflection zero

We theoretically describe and numerically investigate the operation of “vectorial” optical differentiation of a three-dimensional light beam, which consists in simultaneous computation of two partial derivatives of the incident beam profile with respect to two spatial coordinates in different transverse electric field components. It is implemented upon reflection of the beam from a layered structure by simultaneously utilizing the effect of optical resonance and the spin Hall effect of light. As an example of a layered structure performing this operation, we propose a three-layer metal–dielectric–metal (MDM) structure. We show that by choosing the parameters of the MDM structure, it is possible to achieve the so-called isotropic vectorial differentiation, for which the intensity of the reflected optical beam (squared electric field magnitude) is proportional to the squared absolute value of the gradient of the incident linearly polarized beam. The presented numerical simulation results demonstrate high-quality vectorial differentiation and confirm the developed theoretical description.

Two Distinct Charge Orders in Infinite-Layer PrNiO2+δ Revealed by Resonant X-Ray Diffraction

Abstract Research of infinite-layer nickelates has unveiled a broken translation symmetry, which has sparked significant interest in its root, its relationship to superconductivity, and its comparison to charge order in cuprates. In this study, resonant x-ray scattering measurements were performed on thin films of infinite-layer PrNiO2+δ . The results show significant differences in the superlattice reflection at the Ni L 3 absorption edge compared to that at the Pr M 5 resonance in their dependence on energy, temperature, and local symmetry. These differences point to two distinct charge orders, although they share the same in-plane wavevectors. It is suggested that these dissimilarities could be linked to the excess oxygen dopants, given that the resonant reflections were observed in an incompletely reduced PrNiO2+δ film. Furthermore, azimuthal analysis indicates that the oxygen ligands likely play a crucial role in the charge modulation revealed at the Ni L 3 resonance.

Two-dimensional viscous study of coupled nonlinear fluid resonances in two narrow gaps

The wave-induced hydrodynamics of coupled nonlinear piston-mode fluid resonances within two narrow gaps between three barges are numerically investigated using a two-dimensional viscous wave flume. This study aims to explore the time-dependent nonlinear interactions between fluid oscillations in the two gaps. The coupled synchronous dynamic behaviors of fluid oscillations during the transient evolution stage are first examined in terms of amplitude and frequency modulation. It is shown that phase dynamics, including phase slipping, trapping, and locking, play significant roles in establishing the coupled synchronous dynamic evolutions of fluid oscillations in the two gaps. The quasi-steady state of the amplitude- and phase-frequency responses of fluid oscillations within the gaps, along with the reflection and transmission waves in front of and behind the three-barge system, are further analyzed. This analysis clarifies the significance of viscous damping energy dissipation and radiation damping energy transfer involved in gap resonance problems. This clarification also explains the performance of fully nonlinear potential flow solvers in predicting fluid resonances in the two narrow gaps. Finally, the nonlinear dynamic features of fluid oscillations are examined. The effects of incident wave nonlinearity, i.e., wave steepness, on resonant frequencies, response amplitudes, energy dissipation, and reflection and transmission coefficients are investigated. Harmonic analysis via Fourier transformation reveals the contributions of first-, second-, and third-order harmonics to the overall response amplitudes. The physical insights gained from this study provide a deeper understanding of the coupled nonlinear dynamics of piston-mode fluid resonances in multiple narrow gaps.

Research of Turkish Earthquake Reports Based on Resonance Theory

The purpose of this study is to examine the public's perception of the distant suffering of the alienation phenomenon and its treatment in the era of social media. The study uses resonance theory to investigate that the media affects the public perception of distant suffering and elicits moral reflection and emotional resonance in the context of globalization and technological acceleration. This research explains the fundamental ideas of resonance theory, including how to build the axes of resonance and how to look for harmonious resonance in an accelerating society between people and the community. Through the balancing techniques of social media in catastrophe coverage, the paper investigates the case of the Turkish earthquake to demonstrate the reasons for public perception fatigue and the methods by which individuals can get involved in humanitarian efforts.

Music, Exile, and Edward Said: An Interview with Layale Chaker

Abstract The following interview with Layale Chaker, conducted on 14 September 2023, delves into her unique journey as a Palestinian-Lebanese composer, highlighting the pivotal role of music in shaping her sense of “home” following the Lebanese Civil War. Drawing from her diverse musical upbringing, spanning community choirs to formal conservatory education, Chaker elucidates the disparity between institutional training and the lived musical experiences of the Arab world, informing her quest for authenticity in composition. Chaker recounts her involvement with the West-Eastern Divan Orchestra, founded by Daniel Barenboim and Edward Said, juxtaposed with her decision to pursue an individual artistic trajectory. Central to the conversation is her composition “En Présence de l'Absence – Homáge à Edward Saïd,” revealing a deeply personal connection to Said's legacy and a nuanced exploration of his ethos through music. The interview culminates with insights into Chaker's forthcoming opera, “Ruinous Gods,” co-crafted with playwright Lisa Schlesinger. Addressing the profound trauma of refugee children afflicted with uppgivenhetssyndrom (resignation syndrome), the opera promises a poignant musical narrative probing themes of parenthood, displacement, and societal obligation. Set for premiere at the 2024 Spoleto Festival USA, Chaker's work continues to blend artistry with advocacy, offering a resonant reflection on human resilience and responsibility.

Intellectual fitting of hard X-ray resonant reflectance maps obtained for low-contrast oxide multilayers across L absorption edges of Eu and Gd

The present work describes an intellectual computational approach to X-ray resonant reflectometry – a synchrotron-based method aimed at non-destructive characterization of epitaxial nanoscale multilayers with low optical contrast between the sublayer materials. Resonant reflectance from specially designed bilayer structures was measured as a function of grazing angle and photon energy across the L absorption edges of rare earth elements and then modeled with the aid of a specially developed software utilizing OpenCL high speed computations performed on a graphical processing unit. The map fitting was carried out in the blind mode in which the spectral shapes of the optical constants of the sublayers were reconstructed by the fitting routine without initial knowledge of the chemical composition and without using any reference spectra. The model uses stepped Lorentzian line shape for the imaginary part of the scattering length density and the Kramers-Kronig consistent line shape for the corresponding real part. Epitaxially grown Eu2O3 / Gd3Ga5O12 bilayers were used as a test bench system to demonstrate the benefits of the proposed 2D mapping technique over conventional X-ray reflectometry. To increase reliability, the map fitting was carried out simultaneously at the absorption edges of two different chemical elements. The derived shapes and positions of the absorption peaks were used to uniquely identify rare earth elements within the corresponding sublayers and provide information on their oxidation states. The method was experimentally tested on the bilayers having different material order to show that not only the chemical composition but also the layer sequence can be effectively reconstructed in the automatic way from the 2D resonant reflectance maps.

Evaluation of reflective fiber-optic surface plasmon resonance sensor for monitoring scale deposition.

A reflective surface plasmon resonance (SPR) sensor was evaluated for real-time monitoring of scale deposition. The sensor consists of an optical fiber, only 5mm at the gold-coated tip of the sensing area. The effect of silica growth on the sensor response was evaluated using a Na2SiO3 solution. The sensitivity of the sensor to silica was 1.6 ± 0.3nm per one immersion in the solution of 1000mg/L (as SiO2) at 85°Cand subsequnt air drying, as indicated by theSPR peak shift. The amount of silica deposited on the gold surface was measured by the quartz crystal microbalancemethod, and the SPR sensitivity of 0.089nm/ng to silica mass was obtained. The detection limit (3σ) of the SPR sensor was 17ng, correspondingto a thickness of 2.5nm for amorphous silica. The SPR sensor wastested in geothermal brine sampled at the Sumikawa Geothermal Power Plant, where a clear SPR shift was observed, suggesting the effectiveness of the SPR sensor for scale monitoring.

Applicability of energy-theta mapping in resonant soft X-ray reflectometry to probe depth dependence of oxidation state and crystallographic environment in iron oxide multilayers

In the present paper we discuss applicability of the synchrotron method of resonant x-ray reflectometry to non-destructive depth profiling of multilayer heterostructures with low optical contrast between the sublayers. The two-dimensional mapping approach comprising evaluation and measurement of reflectance as a function of photon energy and grazing angle is shown to provide a convenient way to effectively utilize the enhancement of optical contrast between the sublayers that exists at the absorption edges of chemical elements due to particular spectral shape peculiarities related to oxidation state, crystallographic environment and magnetization. In the present study the evaluation of the resonant X-ray reflectivity maps is performed using a specially developed modeling and fitting software. Estimation of the photon energy / grazing angle combinations at which the reflectance is most sensitive to the minor changes in the physical properties of the sublayers is illustrated by the example of ferroic-on-semiconductor nanoscale heterostructures composed of nanoscale film of metallic iron oxidized from either top or bottom side. The subtle differences in resonant soft x-ray reflectance caused by variation of the oxide film thickness, oxidation state and crystallographic environment are discussed. The presented approach is applicable to a large class of heterostructures composed of sublayers that can be distinguished only by the differences in their near edge X-ray absorption fine structure.

Portable, smartphone-linked, and miniaturized photonic resonator absorption microscope (PRAM Mini) for point-of-care diagnostics.

We report the design, development, and characterization of a miniaturized version of the photonic resonator absorption microscope (PRAM Mini), whose cost, size, and functionality are compatible with point-of-care (POC) diagnostic assay applications. Compared to previously reported versions of the PRAM instrument, the PRAM Mini components are integrated within an optical framework comprised of an acrylic breadboard and plastic alignment fixtures. The instrument incorporates a Raspberry Pi microprocessor and Bluetooth communication circuit board for wireless control and data connection to a linked smartphone. PRAM takes advantage of enhanced optical absorption of ∼80 nm diameter gold nanoparticles (AuNP) whose localized surface plasmon resonance overlaps with the ∼625 nm resonant reflection wavelength of a photonic crystal (PC) surface. When illuminated with wide-field low-intensity collimated light from a ∼617 nm wavelength red LED, each AuNP linked to the PC surface results in locally reduced reflection intensity, which is visualized by observing dark spots in the PC-reflected image with an inexpensive CMOS image sensor. Each AuNP in the image field of view can be easily counted with digital resolution. We report upon the selection of optical/electronic components, image processing algorithm, and contrast achieved for single AuNP detection. The instrument is operated via a wireless connection to a linked mobile device using a custom-developed software application that runs on an Android smartphone. As a representative POC application, we used the PRAM Mini as the detection instrument for an assay that measures the presence of antibodies against SARS-CoV-2 infection in cat serum samples, where each dark spot in the image represents a complex between one immobilized viral antigen, one antibody molecule, and one AuNP tag. With dimensions of 23 × 21 × 10 cm3, the PRAM Mini offers a compact detection instrument for POC diagnostics.

Electromagnetic wave absorption performance of porous geopolymer: Dual effects of fly ash on alkali activation and microwave dissipation

The simultaneous occurrence of aggregation reactions in fly ash (FA) facilitates the uniform dispersion of internal ferrite into the geopolymer. Considering the excellent impedance matching and multiple reflection effects of foam concrete, this paper develops a ‘zero-absorber’ foam geopolymer-based electromagnetic absorbing material. The effects of different densities (400, 600, 800, 1000, 1200 kg/m3) and FA contents (40 %, 50 %, 60 %, 70 %, 80 %) on the electromagnetic absorption performance of foam geopolymer are investigated, respectively. Combined with the iron element distribution and 3D pore structure by SEM and X-CT analysis, the dissipation mechanism of electromagnetic energy by FA and pore structure in foam geopolymer are further explored. Experimental results show that FA can uniformly disperse inherent ferric ions from the matrix into the geopolymer during the polymerization reaction, leading to excellent magnetic losses through magnetic moment orientation adjustment and intermolecular friction interactions without adding external absorber. Additionally, the uniformly dispersed porous structure consumes incident electromagnetic energy through reflection, scattering, coherent attenuation, and interference resonance loss effects. It shows multi-scale electromagnetic absorption effects in the ‘zero-absorber’ foam geopolymer-based electromagnetic absorbing material, including pore structure multiple reflections (millimeter scale), inter-pore wall interference resonance (micrometer scale), and ferric ion magnetic loss (nanometer scale). For the foam geopolymer with 1000 kg/m3 density and 50 % FA, it achieves the optimal electromagnetic absorbing performance with the minimum reflection loss (RL) of −34.9 dB and the effective absorption bandwidth of 14.1 GHz (RL below −10 dB) in 2–18 GHz range.

Photochromism, Thermochromism, and Electrochromism in Solid-State Host-Guest Inclusion Complexes of β-Cyclodextrin with Dialkylcarboxyl-Substituted Viologens.

Multi-stimuli-responsive chromic materials have immense potential for utilization. Herein, two supramolecular inclusion complexes were prepared by self-assembly of β-cyclodextrin (β-CD) with dialkylcarboxyl-substituted viologens, N,N'-di(3-carboxy-propyl)-4,4'-bipyridinium dichloride (CPV·Cl2) and N,N'-di(6-carboxy-hexyl)-4,4'-bipyridinium dibromide (CHV·Br2). The self-assembled inclusion complexes CPV2+@β-CD and CHV2+@β-CD2 in the solid-state exhibited naked-eye photochromism, thermochromism, and electrochromism in response to multiple external stimuli including light, temperature, and electric field, respectively. Solid-state UV-vis diffuse reflectance and electron spin resonance (ESR) spectroscopy revealed that the observed photochromism, thermochromism and electrochromism are attributed to the formation of viologen free radicals induced by electron transfer under external stimuli. The excellent stimuli-response chromic properties of the title inclusion complexes support their practical utility in visual display, multiple anticounterfeiting, and multilevel information encryption.

Spectroscopy of resonantly saturated selective reflection from high-density rubidium vapor using the pump-probe technique

We study the resonant saturation of selective reflection at the interface between a transparent dielectric and high-density rubidium vapor on the D2-line. Our estimates suggest that, within the selected atomic density range, the dipole–dipole self-broadening of the line can vary from 13.2 to 39.6 GHz. Two tunable lasers are used as sources of pump and probe beams with orthogonal linear polarizations. The selective reflection spectra of the probe laser beam are studied at different atomic densities and pump beam intensities ranging from 0 to 8.8 kW cm−2. At high pump intensities, narrow structures are observed around the pump beam frequency, which are associated with power broadening effects. Increasing the pump intensity reduces the spectral width and the magnitude of the selective reflection resonances. The intensity dependence of the width and the magnitude is measured. By adjusting the pump intensity, it is possible to control the spectral width and reflectivity.

VO2-Based Spacecraft Smart Radiator with High Emissivity Tunability and Protective Layer.

In the extreme space environment, spacecraft endure dramatic temperature variations that can impair their functionality. A VO2-based smart radiator device (SRD) offers an effective solution by adaptively adjusting its radiative properties. However, current research on VO2-based thermochromic films mainly focuses on optimizing the emissivity tunability (Δε) of single-cycle sandwich structures. Although multi-cycle structures have shown increased Δε compared to single-cycle sandwich structures, there have been few systematic studies to find the optimal cycle structure. This paper theoretically discusses the influence of material properties and cyclic structure on SRD performance using Finite-Difference Time-Domain (FDTD) software, which is a rigorous and powerful tool for modeling nano-scale optical devices. An optimal structural model with maximum emissivity tunability is proposed. The BaF2 obtained through optimization is used as the dielectric material to further optimize the cyclic resonator. The results indicate that the tunability of emissivity can reach as high as 0.7917 when the BaF2/VO2 structure is arranged in three periods. Furthermore, to ensure a longer lifespan for SRD under harsh space conditions, the effects of HfO2 and TiO2 protective layers on the optical performance of composite films are investigated. The results show that when TiO2 is used as the protective layer with a thickness of 0.1 µm, the maximum emissivity tunability reaches 0.7932. Finally, electric field analysis is conducted to prove that the physical mechanism of the smart radiator device is the combination of stacked Fabry-Perot resonance and multiple solar reflections. This work not only validates the effectiveness of the proposed structure in enhancing spacecraft thermal control performance but also provides theoretical guidance for the design and optimization of SRDs for space applications.

Influence of high-temperature thermal annealing on paramagnetic point defects in silicon-rich silicon nitride films formed in a single-wafer-type low-pressure chemical vapor deposition reactor

The influence of high-temperature thermal annealing on silicon dangling bonds called K centers in Si-rich silicon nitride films grown in a single-wafer-type low-pressure chemical vapor deposition reactor with the SiH2Cl2-NH3 system at 750 °C has been investigated by combining thermal desorption spectroscopy (TDS), Fourier transform infrared spectroscopy-attenuated total reflection, spectroscopic ellipsometry, and electron spin resonance. In the TDS analysis, H2 desorption from the nitride films was detected above about 600 °C. It is found that thermal annealing at 750 and 900 °C caused a slight decrease in the K center density and a change in the g value of K centers, which are considered to be caused by changes in the atomic structure of the nitride films. On the other hand, thermal annealing at 1050 °C resulted in a substantial decrease in the K center density and the generation of paramagnetic defects with unprecedented characteristics. The findings in this study are expected to provide important guidelines for the design of manufacturing processes of nonvolatile memories.

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.