Resonant Reflection Research Articles

Modeling the Propagation of Fast Magnetosonic Waves and Their Conversion to Electromagnetic Ion Cyclotron Waves at Low L Shells

AbstractThe propagation of fast magnetosonic (MS) waves from high to extremely low L shells and their conversion into electromagnetic ion cyclotron (EMIC) waves is investigated with a ray tracing model and a full‐wave model. The ray tracing simulations show that MS waves in the vicinity of the local crossover frequency at low L shells have a latitudinal range from to with wave normal angles from to , both of which provide the opportunity for their mode conversion to EMIC waves. Results from ray tracing are fed into the full‐wave model as initial conditions. The full‐wave simulations show that the incoming MS waves with small () and intermediate () wave normal angles may be efficiently converted to right‐handedly polarized band EMIC waves, which may be further converted to right‐handedly polarized band EMIC waves or to guided left‐handedly polarized band EMIC waves through bi‐ion resonance reflection and polarization reversal. With intermediate () or larger wave normal angles, via polarization reversal and left‐handed polarization cut‐off reflection, the incoming MS waves may be efficiently converted to guided left‐handedly polarized band EMIC waves and the optimal wave normal angles corresponding to the maximum conversion efficiencies decrease with magnetic latitudes. Our study verifies the mode conversion mechanism of MS waves to EMIC waves proposed with a previous ray tracing study and examines the dependence of the efficiency of the wave energy transfer on the magnetic latitudes and wave normal angles, which may help to understand the wave properties and distribution of MS and EMIC waves observed at extremely low L shells.

3D Architectural MXene‐based Composite Films for Stealth Terahertz Electromagnetic Interference Shielding Performance

AbstractThe terahertz frequency range is gaining popularity in security, stealth technology, and the future 6G network communication. For the control of severe terahertz electromagnetic interference (EMI) pollution, frequency‐selective stealth‐capable shielding materials are being explored to mask terahertz signals. For the realization of masking terahertz signals, the robustness, lightweight, and shape‐conformable materials with excellent terahertz EMI shielding/absorption are crucial. Here, the study reports the fabrication of 3D symmetric pyramidal architectural MXene composite films with frequency‐selective stealth performance characteristics via the facile drop casting method. With the high absorption capability of 2D MXene layers, the MXene composite films exhibit substantial terahertz stealth performance. 3D pyramidal microstructure design leads to frequency selective surface‐assisted reflection resonance in the frequency range of 0.6–1.1 THz. The MXene composite film demonstrates an outstanding maximum terahertz shielding effectiveness (SE) of up to 70.4 dB and a specific SE of 0.55 dB µm−1. These terahertz SE values exceed all of those for MX‐based shielding material designs reported in the literature. The investigation will open a new direction toward developing terahertz EMI shielding thin films with easy integration into any surface for stealth capabilities.

Integrated microcavity optomechanics with a suspended photonic crystal mirror above a distributed Bragg reflector.

Increasing the interaction between light and mechanical resonators is an ongoing endeavor in the field of cavity optomechanics. Optical microcavities allow for boosting the interaction strength through their strong spatial confinement of the optical field. In this work, we follow this approach by realizing a sub-wavelength-long, free-space optomechanical microcavity on-chip fabricated from an (Al,Ga)As heterostructure. A suspended GaAs photonic crystal mirror is acting as a highly reflective mechanical resonator, which together with a distributed Bragg (DBR) reflector forms an optomechanical microcavity. We demonstrate precise control over the microcavity resonance by change of the photonic crystal parameters. We find that the microcavity mode can strongly couple to the transmissive modes of the DBR. The interplay between the microcavity mode and a guided resonance of the photonic crystal modifies the cavity response and results in a stronger dynamical backaction on the mechanical resonator compared to conventional optomechanical dynamics.

Glucose Concentration Monitoring Using Microstrip Spurline Sensor

Abstract This article reports a microstrip spurline sensor for glucose concentration monitoring. The microstrip spurline sensor is a low-cost and easy-to-fabricate device that uses printed circuit board (PCB) technology. It consists of a combination of four spurlines and transmission lines. The four spurlines are used to reject unwanted frequencies, while the transmission lines allow the desired frequencies to pass through. The resonance frequency (Fr) and reflection coefficient (S11) were recorded through meticulous simulations and experiments over a frequency range from 1.5 GHz to 4 GHz. In addition, the sensor was used to detect changes in glucose concentration, ranging from 0 mg/dL to 150 mg/dL. The findings of this study show that the antenna-based sensor proposed in this research can effectively measure glucose levels across the diabetes range, from hypoglycemia to normoglycemia to hyperglycemia, with a high degree of sensitivity of 7.82 x 10−3 dB/(mg/dL) and 233.33 kHz/(mg/dL).

Mechanically Driven Solidly Mounted Resonator‐Based Nanoelectromechanical Systems Magnetoelectric Antennas

The miniaturization of antennas has been a significant challenge in the field of electronics and telecommunications. In recent years, mechanically driven thin‐film bulk acoustic resonator (FBAR) magnetoelectric (ME) antennas have emerged as a promising solution, demonstrating superior miniaturization capabilities compared to conventional state‐of‐the‐art compact antennas. While nanoelectromechanical systems (NEMS) FBAR ME antennas exhibit high miniaturization potential, their suspended thin‐film heterostructures render them fragile and exhibit low power handling capabilities. The findings demonstrate that solidly mounted resonator (SMR) NEMS ME antennas on a Bragg acoustic resonant reflector offer a compelling solution. With a circular resonating disk of 200 μm diameter operating at 1.75 GHz, these SMR‐based antennas display a high antenna gain of −18.8 dBi and a 1 dB compression point (P1dB) of 30.4 dBm. Compared to same‐size FBAR ME antennas with a free‐standing membrane, SMR‐based antennas exhibit significantly higher structural stability and 23.3 dB stronger power handling capability, in addition to easier fabrication processes. The compatibility of the simple fabrication processes with complementary metal–oxide–semiconductor technology, along with the dramatic miniaturization, high power handling, robust mechanical properties, and much higher antenna radiation gain, make these SMR‐based ME antennas a promising candidate for future antenna systems.

Phosphorous-containing flame retardant plasticizer based on Cassia fistula seed oil and their application in poly(vinyl chloride) films

The need for safety and sustainability has prompted the development of flame-retardant bio-based plasticizers from renewable resources. In this study, an efficient phosphorous-containing flame retardant plasticizer (ECFSO-P) for poly(vinyl chloride) (PVC) was synthesized using Cassia fistula seed oil and characterized by fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and proton nuclear magnetic resonance (1H NMR) spectroscopies. In replace of the dioctyl phthalate (DOP), the ECFSO-P was employed as a flame retardant plasticizer to produce poly(vinyl chloride) (PVC) blends. The PVC blends were prepared using ECFSO-P, DOP, and ECFSO-P + DOP blends as plasticizers. The PVC blends with different concentrations of DOP and ECFSO-P were investigated with thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), mechanical properties, fire retardant performance, crystallinity, leaching, volatility, and density functional theory (DFT) studies. The TGA results showed that the thermal degradation temperature of PVC blends plasticized with ECFSO-P reached 230.6 ºC. The glass transition temperature, Tg decreased to 34ºC as determined by DSC, when DOP was completely replaced with ECFSO-P. When PVC was plasticized with ECFSO-P only, the tensile strength and elongation at break reached 6.41 and 508.83, respectively. The leaching and volatility properties of ECFSO-P plasticized PVC blends were better than DOP plasticized film. Limited oxygen index (LOI) and smoke density rating (SDR) values were increased by 6.7% and 17.4%, respectively. The WAXS profiles showed that ECFSO-P did not alter the order of crystallinity among the PVC chains. As expected, the hydrogen bonding interactions between plasticizers and the -CH-Cl units of PVC were confirmed by DFT calculations.

Composition Dictates Molecular Orientation at the Heterointerfaces of Vapor-Deposited Glasses.

Physical vapor deposition (PVD) can prepare organic glasses with a preferred molecular orientation. The relationships between deposition conditions and orientation have been extensively investigated in the film bulk. The role of interfaces on the structure is less well understood and remains a key knowledge gap, as the interfacial region can govern glass stability and optoelectronic properties. Robust experimental characterization has remained elusive due to complexities in interrogating molecular organization in amorphous, organic materials. Polarized soft X-rays are sensitive to both the composition and the orientation of transition dipole moments in the film, making them uniquely suited to probe molecular orientation in amorphous soft matter. Here, we utilize polarized resonant soft X-ray reflectivity (P-RSoXR) to simultaneously depth profile the composition and molecular orientation of a bilayer prepared through the physical vapor deposition of 1,4-di-[4-(N,N-diphenyl)amino]styryl-benzene (DSA-Ph) on a film of aluminum-tris(8-hydroxyquinoline) (Alq3). The bulk orientation of the DSA-Ph layer is controlled by varying deposition conditions. Utilizing P-RSoXR to depth profile the films enables determination of both the bulk orientation of DSA-Ph and the orientation near the Alq3 interface. At the Alq3 surface, DSA-Ph always lies with its long axis parallel to the interface, before transitioning into the bulk orientation. This is likely due to the lower mobility and higher glass transition of Alq3, as the first several monolayers of DSA-Ph deposited on Alq3 appear to behave as a blend. We further show how orientation at the interface correlates with the bulk behavior of a codeposited glass of similar blend composition, demonstrating a straightforward approach to predicting molecular orientation at heterointerfaces. This work provides key insights into how molecules orient during vapor deposition and offers methods to predict this property, a critical step toward controlling interfacial behavior in soft matter.

The value of pre-symptomatic genetic risk assessment for age-related macular degeneration: the Moran AMD Genetic Testing Assessment (MAGENTA) study—a study protocol for a randomized controlled trial

BackgroundAge-related macular degeneration (AMD) is an irreversible blinding eye condition with complex genetic and environmental etiologies. Genetic testing for AMD for previously identified multiple-risk single nucleotide polymorphisms can help determine an individual’s future susceptibility. However, such testing has been discouraged until evidence shows that providing such information to symptomatic or pre-symptomatic individuals will alter their disease course. Therefore, we designed this study to investigate whether knowledge of AMD risk could stimulate the adoption of a healthier lifestyle that could lower the incidence of AMD later in life. We hypothesize that pre-symptomatic individuals informed of a high genetic risk of AMD are more likely to make quantifiable, positive lifestyle changes relative to participants informed of lower genetic risk or randomized to deferred disclosure of genetic testing results.MethodsThe Moran AMD Genetic Testing Assessment (MAGENTA) study is a phase 2, single-center, prospective, double-masked, randomized controlled trial conducted at the John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. Participants are randomized by a 3:1 allocation ratio to immediate and deferred disclosure groups and followed for 12 months. Skin, ocular, and serum carotenoid status, as well as nutritional and social surveys, are assessed at study visits. Skin carotenoid assessment is by resonance Raman spectroscopy and reflectance spectroscopy, ocular carotenoids are measured with Heidelberg Spectralis autofluorescence imaging and fluorescence lifetime imaging ophthalmoscopy (FLIO), and serum carotenoids are quantified using high-performance liquid chromatography. The primary outcome evaluates changes in skin carotenoid status in response to genetic risk disclosure. The secondary outcomes examine changes in ocular and serum carotenoid status in response to genetic risk disclosure. Also, we will correlate AMD genetic risk with baseline ocular and systemic carotenoid status and FLIO.DiscussionMAGENTA will provide much-needed evidence on whether pre-symptomatic testing for AMD risk can lead to quantifiable long-term changes in behavior and lifestyle associated with a lower incidence of AMD later in life. Findings from the MAGENTA trial will facilitate the design of a future larger, longer-term, multicenter phase 3 trial that could feature subgroup analysis, expanded measures of lifestyle modification, and potential active nutritional interventions.Trial registrationClinicalTrials.gov NCT05265624. Registered on March 3, 2022.

Multiresonant Nonlocal Metasurfaces.

Optical metasurfaces supporting localized resonances have become a versatile platform for shaping the wavefront of light, but their low quality (Q-) factor modes inevitably modify the wavefront over extended momentum and frequency space, resulting in limited spectral and angular control. In contrast, periodic nonlocal metasurfaces have been providing great flexibility for both spectral and angular selectivity but with limited spatial control. Here, we introduce multiresonant nonlocal metasurfaces capable of shaping the spatial properties of light using several resonances with widely disparate Q-factors. In contrast to previous designs, the narrowband resonant transmission punctuates a broadband resonant reflection window enabled by a highly symmetric array, achieving simultaneous spectral filtering and wavefront shaping in the transmission mode. Through rationally designed perturbations, we realize nonlocal flat lenses suitable as compact band-pass imaging devices, ideally suited for microscopy. We further employ modified topology optimization to demonstrate high-quality-factor metagratings for extreme wavefront transformations with large efficiency.

Sensing mechanism of an Au-TiO2-Ag nanograting based on Fano resonance effects.

In recent years, with the development of nano-photonics, Fano resonance has gained increasing attention. Due to its high sensitivity, real-time detection, and label-free properties, the Fano resonance sensor has been widely applied in the fields of biochemistry and environmental detection. To improve the sensing characteristics of Fano resonance, an A u-T i O 2-A g grating structure is proposed in this paper, and the sensing performance is enhanced by a bi-metallic grating and deposited T i O 2. The characteristics of both sensing and field distribution of the model are accordingly analyzed using the finite-difference time-domain method. By varying the structural parameters such as grating period, grating height, silver film thickness, and T i O 2 layer thickness, the tuning of sensing characteristics can be realized, and afterwards, the sensing performance is improved; consequently, the Fano resonance reflection spectrum with high sensitivity and a high figure of merit (FOM) value is obtained. When the grating period P=200nm, grating height T1=90nm, silver film thickness T2=20nm, T i O 2 layer thickness T3=20nm, and S i O 2 layer thickness T4=600nm, such a structure indicates favorable sensing performance, and sensor detection accuracy can reach 10-3; maximum sensitivity is 1400nm/RIU, and maximum FOM can reach 4212R I U -1. The results demonstrate that the designed Fano resonance sensing model has good potential for application.

Insights into the formation and stability of soil aggregates in relation to the structural properties of dissolved organic matter from various organic amendments

Organic matter is an important determinant of soil aggregate formation and stability. However, the role of its structure, especially that of dissolved organic matter (DOM) from organic amendments (OAs), in the aggregation process remains imprecise. The purpose of this study was to understand the relationship between the chemical structure of water-extractable organic matter (WEOM), potential source of DOM from OAs, and their aggregate formation/stability functionality through model experiment. The WEOM samples were prepared from bark compost (BC), coffee residue compost (CRC), cattle manure compost (CMC), sewage sludge compost (SSC), fish cake (FC), and rapeseed oil cake (ROC) and characterized using high-performance size exclusion chromatography and 13C nuclear magnetic resonance and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies. An upland field soil was packed in glass columns and each WEOM solution or ultrapure water (Control) was applied repeatedly during a 30-day period. Aggregate size distribution (>2000, 500–2000, 250–500, 53–250, and <53 µm) was then measured and aggregate stability indices, mean weight diameter (MWD), and geometric mean diameter (GMD) were calculated. The addition of WEOM increased the distributions of soil mass and soil organic carbon (C) into the > 2000 µm aggregate fraction compared to Control treatment, and the ROC-, CRC-, and SSC-WEOM treatments resulted in greater MWD and GMD than Control and/or the other WEOM treatments. The % O-alkyl C (29–59% of total C) and the relative abundance of high-molecular-weight (HMW) fraction (>10 kDa; 2.3–7.1% of total) in WEOM correlated positively with the proportion of > 2000 µm aggregate fraction. The relative abundance of HMW fraction also correlated positively with MWD. These findings suggest that the high amounts of polysaccharides, suggested by % O-alkyl C and supported by DRIFT spectra, and/or other HMW components are desirable structural characteristics of WEOM for promoting macroaggregate formation and aggregate stability.

Measurement of Air Layer Thickness under Multi-Angle Incidence Conditions Based on Ultrasonic Resonance Reflection Theory for Flange Fasteners

During the servicing of flange fasteners, the sealing gasket and the flange cover interface are prone to separation and air contamination due to factors such as stress, corrosion, and vibration. In the detection process, there are two main issues: firstly, the conventional ultrasonic measurement methods based on the theory of acoustic elasticity are not applicable due to the small thickness of the air layer; secondly, the use of conventional vertical incidence detection methods is difficult to ensure due to the influence of the actual structure. To address these issues, this paper first establishes a mathematical model of ultrasonic resonance reflection, and then calculates the corresponding relationship between the air layer thickness and the resonance frequency under vertical incidence conditions. However, this model is difficult to use to calculate the resonance frequency under different incidence angles. To meet the requirements of different working conditions, a finite element simulation model is further established. By comparing the calculation results of the two models under vertical incidence, the reliability of the established finite element model is verified. The reflection and transmission pressure acoustic field distribution under different incidence angles and air layer thicknesses is simulated, and the function relationship between the incidence angle, air layer thickness, and the corresponding first-order resonance frequency is derived. This enables the measurement of the air layer thickness at any incidence angle, providing technical and theoretical support for practical industrial applications.

Inhibition of Strontium Adsorption and Desorption by Ethylenediaminetetraacetic Acid at the Barite (001)–Water Interface

Understanding the sorption behavior of ions at the mineral–water interface is important to determine the fate of elements in the environment. Here, we used barite to understand metal and organic molecule interactions with ionic crystals as organic molecules are used to remove scale that can form during oil recovery in sulfate-rich settings. The sorption behavior of strontium (Sr) on the (001) surface in the presence of ethylenediaminetetraacetic acid (EDTA) was measured using in situ specular X-ray reflectivity (XR) and resonant anomalous X-ray reflectivity (RAXR). Based on the XR results, the presence of EDTA disrupts the barite surface structure, particularly that of the top two monolayers. A maximum of 0.7 (±0.2) EDTA molecules per surface unit cell are adsorbed, though the exact amount cannot be distinguished from that of other adsorbed species, such as Ba2+ and H2O. Based on the RAXR results, the presence of EDTA inhibits Sr incorporation into the barite surface and binds with Sr in solution to limit the amount of Sr2+ in solution. The Sr-EDTA2– complex then binds with barium ions at the barite surface, presumably in a bi-nuclear, bi-dentate state. Desorption of the Sr was also measured in the presence of EDTA. The desorption experiments show that ∼75% of the sorbed strontium was removed following extended reactions with EDTA and deionized water. There were minimal changes in the surface structure following desorption measurements implying that changes following Sr sorption in the presence of EDTA may be irreversible.

Narrowband Thermal Terahertz Emission from Homoepitaxial GaAs Structures Coupled with Ti/Au Metasurface

We report on the experimental evidence of thermal terahertz (THz) emission tailored by magnetic polariton (MP) excitations in entirely GaAs-based structures equipped with metasurfaces. The n-GaAs/GaAs/TiAu structure was optimized using finite-difference time-domain (FDTD) simulations for the resonant MP excitations in the frequency range below 2 THz. Molecular beam epitaxy was used to grow the GaAs layer on the n-GaAs substrate, and a metasurface, comprising periodic TiAu squares, was formed on the top surface using UV laser lithography. The structures exhibited resonant reflectivity dips at room temperature and emissivity peaks at T=390 °C in the range from 0.7 THz to 1.3 THz, depending on the size of the square metacells. In addition, the excitations of the third harmonic were observed. The bandwidth was measured as narrow as 0.19 THz of the resonant emission line at 0.71 THz for a 42 μm metacell side length. An equivalent LC circuit model was used to describe the spectral positions of MP resonances analytically. Good agreement was achieved among the results of simulations, room temperature reflection measurements, thermal emission experiments, and equivalent LC circuit model calculations. Thermal emitters are mostly produced using a metal-insulator-metal (MIM) stack, whereas our proposed employment of n-GaAs substrate instead of metal film allows us to integrate the emitter with other GaAs optoelectronic devices. The MP resonance quality factors obtained at elevated temperatures (Q≈3.3to5.2) are very similar to those of MIM structures as well as to 2D plasmon resonance quality at cryogenic temperatures.

Competitive spin-flipped normal reflection and equal-spin Andreev reflection in heterojunctions of nodal-line superconductors

The superconducting phase of topological semimetals has become a promising route for the implementation of topological superconductivity and non-Abelian Majorana fermions. Here, we investigate quantum transport in the junctions composed of a nodal-line superconductor, i.e., a topological nodal-line semimetal with superconducting pairing. It is shown that two topologically nontrivial regions exist in the surface Brillouin zone of the nodal-line superconductor labeled by the transverse momentum. Specifically, topological regions with topological invariants $\mathcal{N}=1$ and $\mathcal{N}=2$ host a single and a pair of Majorana zero modes at the surface, respectively. We show that the single Majorana zero mode in the $\mathcal{N}=1$ region can induce resonant equal-spin Andreev reflection, while the Majorana pair in the $\mathcal{N}=2$ region can lead to resonant spin-flipped normal reflection. Both reflection processes can give rise to spin currents but with different polarization directions, whose proportions can be adjusted by a Zeeman field. We also study the transport properties of the device with a sandwich structure and predict that strong crossed Andreev reflection can be implemented with a finite bias. Detection schemes for all these novel transport properties, which can be revealed by spin-resolved transport signatures, are proposed. Our work paves the way for the implementation and detection of Majorana fermions in nodal-line superconductors.

DIFFRACTION OF X-RAYS IN CRYSTALS: A TENSOR APPROACH

The use of X-ray synchrotron radiation makes it possible to observe the polarization, spectral, and angular dependences for diffraction reflections. Their theoretical study calls for application of a tensor approach to describe the interaction of X-rays with atoms of matter. Various representations of the tensor atomic scattering amplitude, results of experimental observations of the anisotropy of resonant X-ray scattering, and the relationship of the electric and magnetic multipole moments on atoms with the properties of forbidden resonant reflections are considered.

Advances in a Microwave Sensor-Type Interdigital Capacitor with a Hexagonal Complementary Split-Ring Resonator for Glucose Level Measurement

This study involved the creation and assessment of a microwave sensor to measure glucose levels in aqueous solutions without invasiveness. The sensor design utilized a planar interdigital capacitor (IDC) loaded with a hexagonal complementary split-ring resonator (HCSRR). The HCSRR was chosen for its ability to generate a highly intense electric field that is capable of detecting variations in the dielectric characteristics of the specimen. A chamber tube was used to fill glucose solutions at the sensor’s sensitive area, and changes in the device’s resonance frequency (Fr) and reflection coefficient (S11) were used to measure glucose levels. Fitting formulas were developed to analyze the data, and laboratory tests showed that the sensor could accurately measure glucose levels within a range of 0–150 mg/dL. At a concentration of 37.5 mg/dL, the sensitivity based on S11 and Fr reached maximum values of 10.023 dB per mg/dL and 1.73 MHz per mg/dL, respectively. This implies that the sensor put forward has the possibility of being utilized in medical settings for the monitoring of glucose levels.

Numerical investigation on the mitigation of harbor oscillations by periodic undulating topography

Mitigation of harbor oscillations is a crucial concern in coastal engineering. It is more economical and accessible for an established harbor to reduce the intensity of oscillations by changing the incident wave conditions rather than modifying the harbor layout. Periodic sandbars and sand ripples, which are common in nearshore zones, can be modified into submerged breakwaters. When the wavelength of the bottom undulations is approximately half of the incident wavelength, the resonant reflection (i.e., Bragg reflection) appears, leading to significant enhancements in wave reflection, which further results in the reduction of the incident wave energy.The present study evaluates the effectiveness of Bragg reflection in inhibiting harbor oscillations using an extended mild-slope equation. The results show that undulating seabed topography outside the harbor can significantly weaken the intensity of the harbor oscillations. Subsequently, a possible mitigation mechanism is proposed. The influences of the bar wavelength, bar number, bar height, and the slope of seabed on the mitigation effect of harbor oscillations are studied. Furthermore, it is found that the optimal mitigation effect for different resonant modes is not constant, and the reason for this is explained.

Andreev processes in mesoscopic multiterminal graphene Josephson junctions

There is growing interest in using multi-terminal Josephson junctions (MTJJs) as a platform to artificially emulate topological phases and to investigate complex superconducting mechanisms such as quartet and multiplet Cooper pairings. Current experimental signatures in MTJJs have led to conflicting interpretations of the salient features. In this work, we report a collaborative experimental and theoretical investigation of graphene-based four-terminal Josephson junctions. We observe resonant features in the differential resistance maps that resemble those ascribed to multiplet Cooper pairings. To understand these features, we model our junctions using a circuit network of coupled two-terminal resistively and capacitively shunted junctions (RCSJs). Under appropriate bias current, the model predicts that a current flowing between two diagonal terminals in a four-terminal geometry may be represented as a sinusoidal function of a weighted sum of the superconducting phases. We show that starting from a semi-classical model with diffusive current-phase relations, the MTJJ effectively emulates a general form of the expected current-phase relation for multiplet Cooper pairings. Our study therefore suggests that differential resistance measurements alone are insufficient to conclusively distinguish resonant Andreev reflection processes from semi-classical circuit-network effects.

Sc2O3 on sapphire all-crystalline grating–waveguide resonant reflectors

This paper reports the fabrication and first demonstration of all-dielectric crystalline grating–waveguide reflectors comprising a Sc2O3 waveguide grown on a sub-wavelength-patterned sapphire substrate. Rigorous coupled-wave analysis is employed to simulate the operation of the structure, suggesting a 100% resonance reflectivity in theory. Structuring of the sapphire substrate is achieved using inductively coupled plasma etching, whilst pulsed laser deposition is used for epitaxial growth of the Sc2O3 crystalline waveguide. Devices with distinct TE- and TM-polarisation resonances around 1030-nm for an angle of incidence near 10° are demonstrated, with reflectance approaching 90%. The discrepancy in reflectivity is attributed to the waveguide thickness variation and surface roughness. Refinement of the fabrication processes and tolerances should lead to improvement in the surface quality of the crystalline grating–waveguide structure and operation closer to the ideal resonance reflectivity.