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The larger electric or magnetic Purcell factor demonstrates that the structure can be utilized as an electric or magneto-optical emission project. Their simultaneous realization offers the potential for integrated circuits to achieve selective photon sources. In this study, we put forth a proposal for the simultaneous attainment of substantial electrical and magnetic Purcell enhancements. In our hybrid metal–dielectric metasurface, the toroidal dipole (TD) quasi bound states in the continuum mode and the electric dipole (ED) mode are strongly coupled, so the hybrid mode combines the advantages of both, with a large Q factor and a small mode volume. The design implements a Rabi splitting energy of 222 meV between the TD quasi-BIC and ED modes, achieving an electric Purcell factor of 43 and a magnetic Purcell factor of 684, which are greater than those observed for the metal rod and dielectric structure, respectively. This paves the way for the development of high-performance hybrid optoelectronic applications. [ABSTRACT FROM AUTHOR]

We report a plasmonic–dielectric metasurface that offers dynamic control over chiroptical properties, adjustable Q-factors, and inter-band chirality manipulation through multiple symmetry-breaking mechanisms. By controlling chiral quasi-bound states in the continuum (BIC) modes and Fano resonances, we enable hybridized and independently tunable spectral responses, offering precise control over resonance amplitude, polarization sensitivity, and refractive index sensing with high flexibility. Chirality is induced by rotating silicon nanofins on a dielectric spacer with a gold backplate, enabling tunable chiroptical responses with controllable spectral linewidth and independent or simultaneous dual-wavelength band excitation. We report a novel phenomenon of controlling interplay of chirality between two closely positioned wavelength bands to tailor symmetry breaking for a specific resonant mode (chiral) while preserving symmetry for the other mode (achiral). Additionally, we report the phase-sensitive evolution of Fano resonance from pure reflectance dip when controlled by dielectric spacer height and further demonstrated phase-insensitive control of Fano resonance amplitude. We divided Fano resonance into a distinct spectral peak and dip to improve light manipulation within the metasurface. Our proposed sensor demonstrates sensitivity and a quality factor of about 435 nm/RIU and 3888, respectively. Furthermore, we compared different phenomena (chiral selectivity, quasi-BIC, Fano) and sensing parameter values for different metasurface configurations (including single nanofin and absence of a spacer) and observed that the configuration without a spacer achieved the highest sensitivity of approximately 640 nm/RIU. [ABSTRACT FROM AUTHOR]

Unilateral radiating antennas are widely studied due to their ability to provide lateral or unidirectional radiation patterns, which are especially suitable for indoor and office Wi-Fi router applications. In this letter, a unilateral radiating rectangular dielectric resonator antenna (DRA) without a ground plane is proposed. A temperature stable low-loss 0.8MgTiO3–0.2Mg2SiO4–0.06CaTiO3 (MT–MS–CT) composite ceramic prepared via solid-state reaction and sintered at 1380 °C is utilized for the proposed DRA. Notably, the MT–MS–CT composite ceramic shows good dielectric performance with a permittivity of ε r ∼ 13 , a quality factor of Q × f 0 ∼ 115 , 000 , Q = 1/dielectric loss, f0 = 8.6 GHz, and a temperature coefficient of resonant frequency T C F ∼ + 4.6 ppm / ° C. Its unilateral radiation pattern is based on the complementary magnetic dipole and electric dipole, where the excited dominant TE111 mode of the rectangular DRA serves as the magnetic dipole and a probe acts as an electric dipole. The proposed prototype antenna fabricated using the composite ceramic has a unilateral radiation pattern with wide impedance bandwidth, reasonable gain, and radiation efficiency of 95%. [ABSTRACT FROM AUTHOR]

This paper studies innovative microwave resonators, utilizing special dispersive materials whose relative permittivity is inversely proportional to the frequency square. The "dispersive material" refers not only to natural or synthesized materials but also to equivalent materials achieved through advanced dispersion management techniques. The new resonator theory and analysis of the electromagnetic properties and eigenmode frequency of these new resonators are presented comprehensively and validated through a combination of analytical and numerical simulations using commercially available electromagnetic simulation software (CST Studio Suite). Detailed deduction and demonstration of wideband resonance characteristic, unloaded quality factor (Q), and new formulas are given. Several new types of resonators are introduced including rectangular waveguide cavity resonators and dielectric resonators. This inverse-square property of the special dispersive material provides the new resonators with wideband resonance characteristics. Besides, other dispersive materials whose relative permittivity is inversely proportional to the frequency by the power of n are also demonstrated to be useful for bandwidth enhancement. Moreover, the theory behind these dispersive materials and their equivalent approaches for achieving similar material characteristics through various techniques of dispersion management are also discussed in detail. Compared with the traditional resonator, the new resonator breaks the bandwidth limitation and offers the potential to a variety of new microwave devices and antennas such as bandwidth enhancement, stable radiation patterns, and other merits. This could make it useful for a variety of applications including 6G communication, broadband radar systems, and ultrahigh-speed data transfer. [ABSTRACT FROM AUTHOR]

A bound state in the continuum (BIC) metasurface (MS) was designed to achieve an ultrahigh quality factor(Q factor) using natural hyperbolic materials, such as hexagonal boron nitride. To investigate the structure's dispersion and Q factor, a unit cell of the MS comprising semicircles and rectangles was designed. This MS structure supports symmetry-protected BICs and exhibits a Q factor of approximately 13 000 at 4.43964 × 1013 Hz. By breaking the MS symmetry, the BICs are converted into quasi-BICs, resulting in quasi-BIC resonance with a high Q factor. Further analysis of the reflection spectra and multipole theory indicates that the toroidal dipole (TD) has the most significant influence on the resonance. Thus, the symmetry-protected BIC can be transformed into the TD resonance with a Q factor by breaking symmetry. [ABSTRACT FROM AUTHOR]

We present a model to calculate the resonant energy absorption of a laser with finite number of pulses impinging on a doped porous dielectric slab. Analytical reflection R and transmission T coefficients are first derived as a function of 0 < α ≤ 1 to account for porosity with α = 1 denotes a perfect ideal slab, which are verified using an electromagnetic solver. Based on the Drude model with resonant line due to impurities, we calculate the resonant energy absorption as a function of doping concentration, quality factor of the resonant line, porosity, length of the slab, and laser pulse length. It is important to note that simulating the combined effects of these parameters is challenging using existing models. The energy absorption efficiency is maximized for a certain degree of doping concentration at a given pulse length and also for a certain pulse length at a given doping concentration. At small doping concentration, the absorption efficiency increases with smaller α (high porosity) and the trend is reversed at larger α (low porosity). Dimensionless parameters are constructed, allowing the calculated results to be applicable over a wide range of frequencies and pulse durations. Thus, this model serves as a useful tool to characterize the amount of energy absorption due to these combined effects, which are important for many applications in plasmonics, optoelectronics, high power microwaves breakdown, and organic materials. Some possible experiments are suggested for future verification of the model. [ABSTRACT FROM AUTHOR]

A highly sensitive terahertz stereo metasurface sensor, characterized by a high quality factor (Q-factor) and based on dual toroidal dipole (TD) resonance, has been proposed. The optimal structural parameters are ascertained by comparing the pertinent parameters of the stereo and planar structures in relation to TD modal excitation. The effective excitation of the TD mode is demonstrated using the calculations of multipole scattered power, reflection spectra, surface currents, electric fields, and magnetic field distributions. It is crucial that the stereo metasurface exhibits simplicity and that the dual TD resonance can be readily excited through simple adjustments in the distance and height of the intermediate gap. It also demonstrates exceptionally high sensitivity and Q-factor, both of which are essential for sensing applications. Moreover, the proposed stereo terahertz metasurface sensor still shows excellent sensing performance in a wide range of incidence angles (±40°), which is of great significance for practical applications. In conclusion, this structure offers a novel design framework for high-performance terahertz sensors based on the TD mode. [ABSTRACT FROM AUTHOR]

This study investigates the use of atomic layer deposition (ALD) to mitigate multipacting phenomena inside superconducting radio frequency cavities used in particle accelerators while preserving high quality factors in the 1010 range. The unique ALD capability to control the film thickness down to the atomic level on arbitrary complex shape objects enables the fine-tuning of TiN film resistivity and total electron emission yield (TEEY) from coupons to devices. This level of control allows us to adequately choose a TiN film thickness that provides both high resistivity to prevent Ohmic losses and a low TEEY to mitigate multipacting for the application of interest. The methodology presented in this work can be scaled to other domains and devices subject to RF fields in vacuum and sensitive to multipacting or electron discharge processes with their own requirements in resistivities and TEEY values. [ABSTRACT FROM AUTHOR]

This study investigates the influence of trimming layer thickness on the performance characteristics of thin-film bulk acoustic resonators (FBARs). By adjusting the thickness of the trimming layer, we aimed to optimize the resonant (f s) and antiresonant frequencies (f p) , which are critical for the filter's performance in blocking or passing specific frequency bands. Employing theoretical modeling and experimental validation, we explored how variations in the trimming layer thickness affect the electromechanical coupling coefficient (k t 2) and the overall energy efficiency of FBARs. The study also considered the impact of piezoelectric layer thickness on the effectiveness of these adjustments, revealing that thinner piezoelectric layers are more sensitive to changes in the trimming layer, enhancing the tuning capability for high-frequency applications. Our results confirm that reducing the trimming layer thickness increases both resonant and antiresonant frequencies, with a more pronounced effect on the latter, suggesting a significant phase correction effect from the trimming layer, resulting in the quality Q factor reductions. Our experimental results show that as the trimming layer thickness increases from 200 to 300 nm, the Q factor increases by 11%, while k t 2 decreases by 4%. This research provides critical insights into the design and optimization of FBARs, offering guidelines that can help advance the development of more efficient and effective RF components for future mobile communication technologies. [ABSTRACT FROM AUTHOR]

The optical behavior of the square lattices of the hemispherical nanovoids on the surface of the high-refractive-index all-dielectric slabs in the visible range is studied numerically using gallium phosphide as an example. There exist Fano resonances for these metasurfaces for a limited range of thicknesses. The Fano resonances are caused by the interference between the Mie-type scattering resonances of surface pattern elements and the Fabry–Pérot modes of the slabs. The maximum enhancements of the optical Kerr nonlinearity with respect to the bulk material are revealed at the Fano resonances, in particular, for the thinnest nanostructures. Interestingly, no positive correlation between the quality factor and the enhancement of the optical Kerr effect of the metasurface at the Fano resonances is observed. [ABSTRACT FROM AUTHOR]

Phase separation of biomolecules can facilitate their spatiotemporally regulated self-assembly within living cells. Due to the selective yet dynamic exchange of biomolecules across condensate interfaces, condensates can function as reactive hubs by concentrating enzymatic components for faster kinetics. The principles governing this dynamic exchange between condensate phases, however, are poorly understood. In this work, we systematically investigate the influence of client–sticker interactions on the exchange dynamics of protein molecules across condensate interfaces. We show that increasing affinity between a model protein scaffold and its client molecules causes the exchange of protein chains between the dilute and dense phases to slow down and that beyond a threshold interaction strength, this slowdown in exchange becomes substantial. Investigating the impact of interaction symmetry, we found that chain exchange dynamics are also considerably slower when client molecules interact equally with different sticky residues in the protein. The slowdown of exchange is due to a sequestration effect, by which there are fewer unbound stickers available at the interface to which dilute phase chains may attach. These findings highlight the fundamental connection between client–scaffold interaction networks and condensate exchange dynamics. [ABSTRACT FROM AUTHOR]

We investigate the effect of a cavity on nonlinear two-photon transitions of a molecular system and we analyze how such an effect depends on the cavity quality factor, the field enhancement, and the possibility of dephasing. We find that the molecular response to strong light fields in a cavity with a variable quality factor can be understood as arising from a balance between (i) the ability of the cavity to enhance the field of an external probe and promote multiphoton transitions more easily and (ii) the fact that the strict selection rules on multiphoton transitions in a cavity support only one resonant frequency within the excitation range. Although our simulations use a classical level description of the radiation field (i.e., we solve Maxwell–Bloch or Maxwell–Liouville equations within the Ehrenfest approximation for the field–molecule interaction), based on experience with this level of approximation in the past studies of plasmonic and polaritonic systems, we believe that our results are valid over a wide range of external probing. [ABSTRACT FROM AUTHOR]

Phonons confined in mechanical resonators can be coupled to a variety of quantum systems and are expected to be applied to hybrid quantum systems. Diamond surface acoustic wave (SAW) devices are capable of high efficiency in phonon interaction with color centers in diamond. The temperature dependence of the quality factor is crucial for inferring the governing mechanism of coupling efficiency between phonons and color centers in diamond. In this paper, we report on the temperature dependence of the quality factor of an AlN/diamond SAW device from room temperature to 5 K. The temperature dependence of the quality factor and resonant frequency suggests that the mechanism of SAW dissipation in the AlN/diamond SAW resonator at 5 GHz is the phonon–phonon scattering in the Akheiser regime and that further cooling can be expected to improve the quality factor. This result provides a crucial guideline for the future design of AlN/diamond SAW devices. [ABSTRACT FROM AUTHOR]

This paper proposes an interpretation methodology for the effect of transient process data on quality of injection molded parts. The transient process data measured in the actual processing space have been regarded as the most relevant information to manufacturing processes and product quality. However, its interpretation to pinpoint which feature in the data would affect part quality has traditionally relied on knowledge and understanding of the manufacturing process. The main objective of this method is to reduce the dependency of the transient process data analysis on process knowledge and understanding by using explainable artificial intelligence (XAI). The contribution of the 'section-wise' features in the transient process data to the quality prediction of machine learning (ML) models was investigated for the first time. The interpretation results of the effect of cavity pressure and mold surface temperature on four different quality factors represented reasonable explanations of the characteristics of the polymer materials, product geometry, and molding process. Due to the intermediate relationship of the transient process data with the user-specified process parameters and the resulting quality variables, the interpretation results can be further utilized to optimize the process and provide the optimal transient process data profile for best part quality. [ABSTRACT FROM AUTHOR]

A series of La and Cu co-doped high-density Z-type hexaferrites, namely Ba 3− x La x Co 2 Fe 24− x Cu x O 41 (x = 0.20–0.95 in steps of 0.15), were synthesized via solid-state reaction method. Phase composition, microstructure, static magnetic properties, and high-frequency magneto–dielectric properties were studied systematically. Results show that with the addition of La and Cu, initial Z-type phase gradually transforms into a combination of Z- and W-type phases, and grain size increases. Specific saturation magnetization of samples increases significantly with increasing x and reaches the maximum (σ s = 59.20 emu/g) at x = 0.95. Furthermore, high-frequency magnetic and dielectric properties are improved, with permeability μ ′ and permittivity ε′ becoming almost equal in 0.1–1 GHz band. In particular, the sample with x = 0.65 exhibits excellent Snoek's product, that is (μ ′ − 1) f r ≈ 23.14 GHz , normalized impedance μ ′ / ε ′ approaches 1, and miniaturization factor is around 13.45 (@500 MHz). In this case, dielectric loss tangent tan δ ε is less than 0.003 below 500 MHz, and frequency range in which magnetic quality factor Q is greater than 10 is significantly broadened, covering wide bandwidth from 10 to 580 MHz. Thus, these hexaferrite ceramics are significantly promising for application to microwave communications. [ABSTRACT FROM AUTHOR]

This paper presents a MEMS-based hydrogen sensor that utilizes a cantilever functionalized with palladium. Using rotary electrostatic actuators, the cantilever resonates in in-plane mode which is not complex and compatible with CMOS technology. This sensor works with the lowest viscous damping, and in addition, it is label-free. In the present investigation, solid mechanics module is used for the structural simulation of the sensor. The resulting parameters including oscillation frequency, quality factor, and sensitivity are obtained by the finite element method using 3D simulations. The results show that the quality factor is as high as 1017 at resonance frequency of 305. 25 kHz. Moreover, the resonator sensitivity is about 1 Hz/ppm. • Resonant frequency shift method is studied in order to detect hydrogen gas. • Couette and Stokes models are used to obtain quality factor of the resonator. • The frequency of 305.25 kHz is investigated for in-plane rotational motion. • The quality factor and sensitivity are achieved 1017 and 1 Hz/ppm, respectively. [ABSTRACT FROM AUTHOR]

Resonant ultrasound spectroscopy (RUS) is a non-destructive technique to calculate material elastic constants from resonant frequencies. However, low quality factor (i.e., low-Q) materials experience strong energy attenuation during vibration, resulting in the overlap and partial loss of resonant peaks in experimental spectra. Consequently, extracting authentic resonant frequencies becomes challenging, making the subsequent elastic constant calculation time-intensive and necessitating expert intervention. Regarding this, a novel RUS method using convolutional neural networks (CNN) is proposed. This method circumvents the traditional frequency extraction step and enables rapid and automated estimation of elastic constants for low-Q materials directly from the experimental spectra. The CNN model was designed to take real parts of the resonant spectra and mass density as inputs, outputting the material's independent elastic constants. Leveraging a simulation dataset for training, the model's feasibility was demonstrated by characterizing five elastic constants of a composite material with a Q of approximately 25. The trained model performed well on both the simulated test set and three real-world samples, achieving a sample proportion of 96.5% in the test set with all relative errors of elastic constants falling within 10%. This study contributes a fresh perspective to efficiently estimating elastic constants in RUS, particularly for low-Q materials. [ABSTRACT FROM AUTHOR]

A non-parametric generalized inversion technique for the S -wave amplitude spectrum on both the horizontal and vertical components was adopted to calculate the source parameters, site effects and path attenuations. In this scheme, 1647 three-component records corresponding to 78 earthquakes with M s values of 2.9–6.0 recorded by 58 strong-motion stations in the Sichuan Basin were used. In the non-parametric generalized inversion technique, a reference station was adopted to remove the trade-off between the site and source terms. Then, the simple model R −0.5 was selected to describe the geometric spreading characteristics of the Sichuan Basin region. The frequency-related quality factor models for the horizontal and vertical components are estimated as Q (f) = 129.9872 f  1.1119 and Q (f) = 132.54 f  1.1236, respectively. In addition, the inverted source spectra are well matched with Brune's model, in which the stress drop values range between 0.3 and 3.5 MPa with a mean value of 1.36 MPa. In addition, a comparison between the site effects estimated from horizontal-to-vertical and non-parametric generalized inversion methods shows that the geological environment significantly amplifies the vertical component of ground motion. Finally, a residual related to distance and magnitude indicates that there is no obvious dependence of the scatter on distance or magnitude. The source, path and site parameters estimated in this inversion can be adopted in ground motion simulations, which could aid in the study of seismic disasters and risk assessment in the Sichuan Basin. [ABSTRACT FROM AUTHOR]

The Cu 4 O(PO 4) 2 ceramic with triclinic structure (P-1) was successfully synthesized by hydrothermal and solid-phase reaction process. The influence of the relative density on the dielectric properties and thermal conductivity was systematically investigated. The crystal structure parameters of Cu 4 O(PO 4) 2 ceramics were determined using GSASⅡ software. Based on the P-V-L theory, it is discussed that the dielectric constant of Cu 4 O(PO 4) 2 ceramics is predominantly influenced by the bond ionicity (f i) of Cu-O, and the quality factor is significantly affected the P-O strongly. Concurrently, the P-O bond plays a positive role in the temperature coefficient of the resonance frequency while the Cu-O bond plays a negative role. The quality factor of Cu 4 O(PO 4) 2 ceramic sintered at 850 °C is 23,029 GHz, the dielectric constant is 7.54, and the temperature coefficient of resonance frequency is −103.44 ppm/°C. At the same time, the thermal conductivity of Cu 4 O(PO 4) 2 ceramic sheet is 0.42 W/(m∙K). The research on Cu 4 O(PO 4) 2 ceramic contributes to establishing a new material system for the field of low temperature co-fired ceramics. [ABSTRACT FROM AUTHOR]

Increasing the density of superconducting circuits requires compact components, however, superconductor-based capacitors typically perform worse as dimensions are reduced due to loss at surfaces and interfaces. Here, parallel plate capacitors composed of aluminum-contacted, crystalline silicon fins are shown to be a promising technology for use in superconducting circuits by evaluating the performance of lumped element resonators and transmon qubits. High aspect ratio Si-fin capacitors having widths below 300 nm with an approximate total height of 3 μm are fabricated using anisotropic wet etching of Si(110) substrates followed by aluminum metallization. The single-crystal Si capacitors are incorporated in lumped element resonators and transmons by shunting them with lithographically patterned aluminum inductors and conventional Al/AlOx/Al Josephson junctions respectively. Microwave characterization of these devices suggests state-of-the-art performance for superconducting parallel plate capacitors with low power internal quality factor of lumped element resonators greater than 500 k and qubit T1 times greater than 25 μs. These results suggest that Si-Fins are a promising technology for applications that require low-loss, compact, superconductor-based capacitors with minimal stray capacitance. [ABSTRACT FROM AUTHOR]

This paper introduces an ultrathin, polarization-insensitive, wide angular stable microwave absorber characterized by a high-Quality (Q) factor. The absorber consists of elliptical metallic rings with a thickness of 0.035 mm on the top of Roger’s RT 5880 substrate with a thickness of 0.51 mm and a metallic ground plane with a thickness of 0.035 mm at the bottom. The proposed structure is fourfold symmetric which makes it polarization insensitive. The structure offers angular stability till 60° for the angle of incidence for both Transverse Electric (TE) and Transverse Magnetic (TM) modes under oblique incidence. The structure provides a high-quality factor of 155 at an operating frequency of 7.75 GHz. Also, the structure provides reconfigurability with a change in the axis ratio of the elliptical structure from 7.30 to 9.48 GHz when the axis ratio changes from 0.26 to 0.36 without any change in the unit cell size. The unit cell dimension is 1.07 λg x 1.07 λg x 0.022 λg. With its high Q-factor, thin size, structural simplicity, insensitivity to polarization, and incident angle stability suggested prototype is apt for microwave sensors and antennas to reduce Radar cross-section and X-band satellite communication. [ABSTRACT FROM AUTHOR]

In recent years, metal surface plasmon resonance sensors and dielectric guided-mode resonance sensors have attracted the attention of researchers. Metal sensors are sensitive to environmental disturbances but have high optical losses, while dielectric sensors have low losses but limited sensitivity. To overcome these limitations, hybrid resonance sensors that combine the advantages of metal and dielectric were proposed to achieve a high sensitivity and a high Q factor at the same time. In this paper, a hybrid hollow cylindrical tetramer array was designed, and the effects of the hole radius, external radius, height, period, incidence angle, and polarization angle of the hollow cylindrical tetramer array on the refractive index sensing properties were quantitatively analyzed using the finite difference time domain method. It is found that the position of the resonance peaks can be freely tuned in the visible and near-infrared regions, and a sensitivity of up to 542.8 nm/RIU can be achieved, with a Q factor of 1495.1 and a figure of merit of 1103.3 RIU−1. The hybrid metal–dielectric nanostructured array provides a possibility for the realization of high-performance sensing devices. [ABSTRACT FROM AUTHOR]

For those piezoelectric materials that operate under high-power conditions, the piezoelectric and dielectric properties obtained under small signal conditions cannot be directly applied to high-power transducers. There are three mainstream high-power characterization methods: the constant voltage method, the constant current method, and the transient method. In this study, we developed and verified a combined impedance method that integrated the advantages of the constant voltage and current methods, along with an improved transient method, for high-power testing of PZT-5H piezoelectric ceramics. The results from both methods indicated that with increasing power, the electromechanical coupling coefficient k 31 , the piezoelectric constant d 31 , and the elastic compliance s 11 E of the PZT-5H showed increasing trends, while the mechanical quality factor Q m first decayed rapidly and then stabilized at a fixed level. Additionally, under the combined impedance method, the temperature of the vibrators rose significantly due to self-heating, whereas the transient method generated almost no heat, and the vibrators remained at room temperature. By comparing the results from the two methods, we decoupled the effects of temperature and power on the high-power piezoelectric performance. The results showed that the self-heating temperature amplified the effects of power on k 31 , d 31 , and s 11 E , while its influence on Q m remained negligible. [ABSTRACT FROM AUTHOR]

Being one of the pillars supporting modern industry, the additive manufacturing (AM) field has gone through significant developments over the years, and that is certainly also the case of deposition processes based on the use of the electric arc. However, although most of the knowledge for that specific purpose comes from the more consolidated arc welding counterparts, inherent and yet critical challenges emerge from arc additive manufacturing (Arc-AM). As main advantage, Arc-AM processes offer the capacity to build metallic parts at very high deposition rates and at accessible prices (given their arc welding roots), but generally at the cost of high heat input levels and of tendency for heat accumulation occurrence. Such a negative facet leads to many complications concerning quality factors of the parts, which are related to thermal effects as in terms of geometry/aspect characteristics, distortions, macro/microstructural features, residual stresses, and mechanical properties, and even of production time, invariably in an intertwined connection. The solution, in this case, depends on a large extent on implementations of proper thermal management of the parts being built, which have been indeed the focus of attention of many research and development efforts in the field of Arc-AM over the years as this review aims to present. Thus, the general intent of this work is to contribute to further developments in Arc-AM via a comprehensive review of the related thermal management approaches that have been attempted. The idea is to facilitate the comparison and assessment for suitability of the different thermal management approaches, helping developers working on Arc-AM processes with the foundations for their application and/or improvement. As the subject of thermal management in Arc-AM tends to a more mature scenario, this review ultimately aims at the establishment of a more direct bridge on that matter between academia and industry. Thus, a scientific and hence more critical perspective of the related knowledge is balanced with a technological/engineering and hence more informational side of it. To be representative, it covers information produced over a decade (2013–2022) on scientific and technological developments that somehow have effects via thermal consequences on the metallic layers during the Arc-AM processing time. And it is organized in three main parts. First, in Section 1, after the introduction to the subject of interest and presentation of the general and specific objectives as well as of the scope and delimitations of the review, the complications related to poor thermal management are compiled and discussed in such a way that its importance is characterized and the scientific bases for understanding the functions/effects of the diverse approaches to it are stablished. Then, in Section 2, a systematic bibliometric survey of related publications is presented in detail for auditability and future consultations, and the various thermal management approaches (in fact applied to different Arc-AM processes, metallic materials, and part shapes within the period of analysis) are categorized and then briefly described and representatively discussed in dedicated subsections, which eventually include preliminary remarks and general guidelines for application. The first main section (specifically the part on complications related to poor thermal management) as well as the subsections of the second one were actually built in such a way that they can be consulted individually depending on specific interests of the audience. At the end, in Section 3, the entire subject is recapitulated with combined graphical data, being the main remarks on the thermal management approaches for Arc-AM outlined and the ways by which they are applied to the different deposition processes, materials, and parts globally quantified and characterized. For closure, within the same section, opportunity windows for further developments on thermal management for Arc-AM are finally drawn. Despite the quantity and diversity of approaches identified, as has always been the case in modern manufacturing, the thermal management technology in Arc-AM is expected to keep evolving in the face of new challenges and different scenarios with constant advancements, for which this review will hopefully serve as a relevant source of consultation. [ABSTRACT FROM AUTHOR]

AbstractThis article demonstrates a novel approach to alternating current (AC) magnetic field detection using a yttrium iron garnet (YIG) microsphere combined with magnetostrictive materials. The sensing system utilizes an optical fiber taper to couple light in and out of the YIG microsphere and changes in the transmission spectrum to reflect the magnetic field variations. Three configurations are investigated: YIG microsphere with FeGa sheet, Terfenol-D sheet, and Terfenol-D sheet plus polydimethylsiloxane (PDMS) coating. The system successfully detects AC magnetic fields in the frequency range from 100 to 500 kHz. Initial measurements using FeGa sheets achieved a sensitivity of 107.7 nT/√Hz. Replacing FeGa with Terfenol-D improved the sensitivity approximately three-fold due to its larger magnetostriction coefficient. Further enhancement was achieved by coating the YIG microsphere with PDMS, which improved the optical quality factor by 2.4 times and yielded an optimal sensitivity of 53.51 nT/√Hz at 322.3 kHz. These results demonstrate the potential of YIG microsphere-based systems for high-sensitivity magnetic field detection, offering advantages such as simple structure, low cost, and easy integration. The ability to improve sensitivity through material selection and surface modification suggests promising applications in integrated photonics systems and magnetic field monitoring. [ABSTRACT FROM AUTHOR]

We report on the fabrication and characterization of superconducting magnesium diboride (MgB2) thin films intended for quantum-limited devices based on non-linear kinetic inductance (NLKI) such as parametric amplifiers with either elevated operating temperatures or expanded frequency ranges. In order to characterize the MgB2 material properties, we have fabricated coplanar waveguide (CPW) transmission lines and microwave resonators using ≈ 40 nm thick MgB2 films with a measured kinetic inductance of ∼ 5.5 pH/ □ and internal quality factors Q i ≈ 3 × 10 4 at 4.2 K. We measure the NLKI in MgB2 by applying a DC bias to a 6 cm long by 4 μm wide CPW transmission line and measuring the resulting phase delay caused by the current dependent NLKI. We also measure the current dependent NLKI through CPW resonators that shift down in frequency with increased power applied through the CPW feedline. Using these measurements, we calculate the characteristic non-linear current parameter, I * , for multiple CPW geometries. We find values for corresponding current density, J * = 12 – 22 MA/cm2, and a ratio of the critical current to the non-linear current parameter, I C / I * = 0.14 – 0.26 , similar to or higher than values for other superconductors such as NbTiN and TiN. [ABSTRACT FROM AUTHOR]

This paper introduces shadow filters that employ multiple-input operational transconductance amplifiers (MI-OTAs) as the active component. Two configurations of shadow filters are proposed. The first configuration, in contrast to previous designs, enables the adjustment of the quality factor without affecting the passband gains of the BPF, LPF, and HPF, thus achieving optimal frequency responses for these filters. The second configuration allows for the variation of the natural frequency without impacting the passband gains of the HPF, LPF, and BPF, maintaining constant passband gains. Moreover, the natural frequency can be electronically controlled by modifying parameters of the original biquad filters, providing advantages in compensating for process, voltage, and temperature variations. The MI-OTA is designed to provide multiple-input differential terminals using the multiple-input bulk-driven MOS transistor (MIBD-MOST) technique, allowing differential input signals to be converted into current output through its transconductance gain. The OTA operates at a supply voltage of 450 mV and consumes 81 nW of power, with the MOS transistors operating in weak inversion. The OTA and shadow filters were designed and simulated using a 0.18 µm CMOS process to validate the functionality and performance of the proposed circuits. [ABSTRACT FROM AUTHOR]

In this work, we employed the transfer-matrix method to obtain the transmittance spectrum of a defective one-dimensional photonic crystal composed of polymer materials. We consider that the dielectric constant of the polymers is a function of the applied pressure, and the cavity is infiltrated by plasma cells. When blood plasma concentration and cavity thickness are increased, we observe a defective mode tuned to long wavelengths within the photonic band gap. By calculating the energy stored in the cavity, a maximization of the quality factor to ∼ 2. 5 5 × 1 0 4 for a 2350 nm cavity was observed. In addition, we report that as the applied pressure increases, the defective mode shifts to shorter wavelengths, accompanied by a decrease in the quality factor to 2. 3 0 × 1 0 4 for a pressure of 100 MPa. [ABSTRACT FROM AUTHOR]

The integration of a photodetector that converts optical signals into electrical signals is essential for scalable integrated lithium niobate photonics. Two-dimensional materials provide a potential high-efficiency on-chip detection capability. Here, we demonstrate an efficient on-chip photodetector based on a few layers of MoTe2 on a thin film lithium niobate waveguide and integrate it with a microresonator operating in an optical telecommunication band. The lithium-niobate-on-insulator waveguides and micro-ring resonator are fabricated using the femtosecond laser photolithography-assisted chemical–mechanical etching method. The lithium niobate waveguide-integrated MoTe2 presents an absorption coefficient of 72% and a transmission loss of 0.27 dB µm−1 at 1550 nm. The on-chip photodetector exhibits a responsivity of 1 mA W−1 at a bias voltage of 20 V, a low dark current of 1.6 nA, and a photo–dark current ratio of 108 W−1. Due to effective waveguide coupling and interaction with MoTe2, the generated photocurrent is approximately 160 times higher than that of free-space light irradiation. Furthermore, we demonstrate a wavelength-selective photonic device by integrating the photodetector and micro-ring resonator with a quality factor of 104 on the same chip, suggesting potential applications in the field of on-chip spectrometers and biosensors. [ABSTRACT FROM AUTHOR]

We propose herein a metamaterial (MM) dual-band THz sensor for various biomedical sensing applications. An MM is a material engineered to have a particular property that is rarely observed in naturally occurring materials with an aperiodic subwavelength arrangement. MM properties across a wide range of frequencies, like high sensitivity and quality factors, remain challenging to obtain. MM-based sensors are useful for the in vitro, non-destructive testing (NDT) of samples. The challenge lies in designing a narrow band resonator such that higher sensitivities can be achieved, which in turn allow for the sensing of ultra-low quantities. We propose a compact structure, consisting of a basic single-square split ring resonator (SRR) with an integrated inverted Z-shaped unit cell. The projected structure provides dual-band frequencies resonating at 0.75 THz and 1.01 THz with unity absorption at resonant peaks. The proposed structure exhibits a narrow bandwidth of 0.022 THz and 0.036 THz at resonances. The resonant frequency exhibits a shift in response to variations in the refractive index of the surrounding medium. This enables the detection of various biomolecules, including cancer cells, glucose, HIV-1, and M13 viruses. The refractive index varies between 1.35 and 1.40. Furthermore, the sensor is characterized by its performance, with an average sensitivity of 2.075 THz and a quality factor of 24.35, making it suitable for various biomedical sensing applications. [ABSTRACT FROM AUTHOR]

The hemispherical resonator gyroscope is a gyroscope based on the principle of Coriolis vibration, widely used in inertial measurement systems of spacecraft. This article decomposes the gyroscope into two parts: the resonator shell and the gyroscope head, establishes the energy dissipation mechanism of the gyroscope, and conducts experimental verification. Firstly, based on the working principle of the gyroscope, a mechanical analysis model of the hemispherical resonator gyroscope head with a resonator spherical shell containing quality defects under second-order vibration state was established. The unbalanced force applied by the resonator spherical shell to the hemispherical resonator gyroscope head was analyzed, and the energy transfer path and dissipation mechanism from the spherical shell to the hemispherical resonator gyroscope head were explained. Finally, through the constructed testing platform, the circumferential quality factor test of the hemispherical resonator gyroscope before and after assembly was completed according to the designed experimental plan, and the consistency between theory and experimental phenomena was verified experimentally. [ABSTRACT FROM AUTHOR]

Alkaline earth metal fluorides, BaF 2 and SrF 2 , are promising low-permittivity ceramics with excellent microwave dielectric properties. However, achieving ideal densifications in BaF 2 and SrF 2 ceramics remains challenging due to their low surface-free energy. In this study, the sintering characteristics of BaF 2 and SrF 2 ceramics are optimized via forming (1– x)BaF 2 - x SrF 2 (x = 0.2, 0.4, 0.5, 0.6, and 0.8) solid solution ceramics. X-ray diffraction (XRD) patterns and Raman spectra provide compelling evidence for successfully forming (1– x)BaF 2 - x SrF 2 solid solutions across the entire composition range. The solid-solution effect significantly enhances densification at a much lower sintering temperature of around 825 °C. Notably, 0.6BaF 2 -0.4SrF 2 ceramics exhibit the optimal microwave dielectric properties with a permittivity (ε r) of 7.26, quality factors (Qf) of 61,006 GHz at 10 GHz and 106,000 GHz at 25 GHz, and a temperature coefficient of resonant frequency (τ f) of −97.46 ppm/°C. Additionally, the advancement of low-temperature co-fired ceramic (LTCC) technology for high-density electronic packaging presents a significant challenge in achieving compatibility between the coefficient of thermal expansion (CTE) of the packaged components. The 0.6BaF 2 -0.4SrF 2 ceramics exhibit a significantly higher CTE of 21.67 ppm/°C compared to most low- ε r ceramics (usually below 10 ppm/°C), resulting in better CTE matching with organic laminates and metal electrodes. Therefore, BaF 2 -SrF 2 solid solution ceramics, addressing the need for low- ε r , high- Qf , and high CTE, offer a potential solution for high-reliability LTCC electronics. [ABSTRACT FROM AUTHOR]

In order to address the energy dilemma and meet environmental protection requirements, it is an urgent need to develop lead-free piezoelectric energy harvesters (PEHs). However, the low output power density has seriously hindered the application of lead-free piezoceramics as high efficiency energy harvesters. To solve above question, the combination of phase structure regulation and texturing technique in the K 0.5 Na 0.5 NbO 3 - x Bi 0.5 Na 0.5 ZrO 3 -0.5%wtBiFeO 3 (KNN- x BNZ) ceramics was adopted in this work. Because of both the Rhombohedral-Orthorhombic-Tetragonal (R-O-T) multiphases coexistence and texturing engineering, an ultrahigh piezoelectric activity quality factor d 33 × g 33 ∼ 18324 × 10−15 m2 N−1 was achieved in the textured KNN-0.05BNZ (T-KNN-0.05BNZ) ceramics, which is about third times higher than that of random KNN-0.05BNZ (R-KNN-0.05BNZ) (d 33 × g 33 ∼ 6672 × 10−15 m2 N−1) ones. A high output power of ∼0.32 mW was also obtained in the T-KNN-0.05BNZ ceramics by cantilever beam-based energy harvester devices under the resonance frequency of 75 Hz and matched R L of 1.2 MΩ, suggesting that the T-KNN-0.05BNZ ceramics have a great potential for application in the PEHs devices. This result also reveals that the combination of phase structure regulation and texturing technique is an effective way to achieved a high energy harvesting performances. [ABSTRACT FROM AUTHOR]

Photonic nanojet can serve as a powerful tool for direct laser micro-machining based on a non-resonance focusing phenomenon. In this study, we propose a photonic nanojet-based direct micro-drilling technique for polymer material with low-cost and low-power continuous-wave laser. The high-quality photonic nanojet is produced using the microcone-shaped probe tip, which is fabricated by the dynamic chemical etching method. By utilizing laser photonic nanojet triggered thermoplasmonics, the high-aspect-ratio microcavity is fabricated with the low threshold value of laser power. The influences of the photonic nanojet peak intensities and distributions on the drilled microcavities are systematically investigated by the experiments and the finite-difference time-domain simulations. With the continuous-wave solid-state laser at a wavelength of 671 nm, the simulations show that the photonic nanojet with a quality factor of 103 is generated at a distance of ~ 20 μm from the surface of the microcone-shaped tip with a beam waist of 252 nm in the x direction, which could overcome the diffraction limit. The experimental results show that the length and peak intensity of the photonic nanojet have increased considerably in the propagation direction by the microcone-shaped probe tip, which leads to form a deep microcavity in the polymer substrate with an aspect ratio of 5.73. The presented microcone-shaped probe tip has potential applications in processing sub-diffraction features with a high aspect ratio. [ABSTRACT FROM AUTHOR]