Quality Factor Of Resonator Research Articles

Robust intrinsic chirality empowered by pair of off-Γ accidental BICs in a triangular lattice metasurface

Abstract Optical chiral metasurfaces with high quality factors enhance light–matter interactions. However, intrinsic chirality based on breaking the symmetry-protected BIC hardly reveals strong circular dichroism (CD) against structural perturbations. Here, we propose a design of the intrinsic chirality empowered by a pair of off-Γ accidental BICs and demonstrate a robust intrinsic chiroptical response continuously exhibiting strong and sign-controllable transmitted CD up to 0.98 and stable high-quality factors under a wide range of perturbations of geometrical parameters. A triangular lattice with slant T-shaped meta-atoms is employed to break all mirror symmetries. The at-Γ quality factor of the chiral resonance is enhanced by four C points and maintains the range of 105–106. Our work is beneficial for designing chiral metasurfaces with a strong intrinsic chirality.

Low frequency quartz tuning fork as hydrogen sensor

The use of hydrogen as a sustainable energy source is pushing the development of innovative sensing strategies for the monitoring of H2 concentration during its production processes and transportation. In this work, we propose a custom quartz tuning fork (QTF) as sensor for the detection of high concentrations of hydrogen in air. The selectivity derives directly from values of molar mass and the viscosity of hydrogen molecules, significantly different from those of the other main constituents of air. Exciting the fundamental flexural mode of a commercially available 12.4 kHz-QTF, we demonstrated the linear dependence of its resonance frequency and quality factor on the H2 concentration, passing through their relationship with molar mass and the viscosity of the H2-air mixture. Monitoring the shift of the resonance frequency of the QTF, the H2-component in air can be estimated with a precision level of 0.74% and accuracy error of 1.82%. The same parameters resulted 0.40% and 4.29%, respectively, when Q values are evaluated. Finally, a beat-frequency approach was proposed to speed up the acquisition in few seconds, monitoring both resonance parameters of the QTF.

Trapping light in air with membrane metasurfaces for vibrational strong coupling

Optical metasurfaces can manipulate electromagnetic waves in unprecedented ways at ultra-thin engineered interfaces. Specifically, in the mid-infrared (mid-IR) region, metasurfaces have enabled numerous biochemical sensing, spectroscopy, and vibrational strong coupling (VSC) applications via enhanced light-matter interactions in resonant cavities. However, mid-IR metasurfaces are usually fabricated on solid supporting substrates, which degrade resonance quality factors (Q) and hinder efficient sample access to the near-field electromagnetic hotspots. Besides, typical IR-transparent substrate materials with low refractive indices, such as CaF2, NaCl, KBr, and ZnSe, are usually either water-soluble, expensive, or not compatible with low-cost mass manufacturing processes. Here, we present novel free-standing Si-membrane mid-IR metasurfaces with strong light-trapping capabilities in accessible air voids. We employ the Brillouin zone folding technique to excite tunable, high-Q quasi-bound states in the continuum (qBIC) resonances with our highest measured Q-factor of 722. Leveraging the strong field localizations in accessible air cavities, we demonstrate VSC with multiple quantities of PMMA molecules and the qBIC modes at various detuning frequencies. Our new approach of fabricating mid-IR metasurfaces into semiconductor membranes enables scalable manufacturing of mid-IR photonic devices and provides exciting opportunities for quantum-coherent light-matter interactions, biochemical sensing, and polaritonic chemistry.

Concept for a geometry-insensitive high-field magnetic resonance detector

AbstractWe introduce an inverse design methodology for a new class of eigenfrequency-invariant metamaterial-resonators, targeting nuclear magnetic resonance detection at ultra-high $$\mathbf {B_0}$$ B 0 field, and operating at two specified frequencies selected from within the 100-1500 MHz range. The primary optimisation goal is to maximise the magnetic field intensity and uniformity within a liquid sample, while the electric energy should be kept to a minimum level to reduce dielectric heating or quadrupolar moment excitation effects. Due to the symmetric geometry requirement of the cavity, a demultiplexer is also designed to direct each discrete resonant signal to another predetermined output port of the resonator. In order to reduce the geometrical dependency of the resonance frequency, a bespoke metamaterial is used for the cavity host. Therefore, an additional optimisation problem for a unit cell domain is defined to seek a proper material layout for the host region of the resonators. Given the sensitivity of the frequency domain, the optimisation process is effectively regulated through the utilisation of both a Helmholtz filter and a projection method. It is found that considerable improvements of the resonator quality factor can be obtained through this optimisation process.

Application of active piezoresistive cantilevers in high-eigenmode surface imaging

Abstract One of the most important limitations of the atomic force microscopy (AFM) is scanning speed, whose high values are required for contemporary high-resolution, long-range diagnostic applications. The measurement bandwidth of an AFM depends on several factors, but usually results from the time constant of the oscillating cantilever, which is correlated with its resonance frequency and quality factor. We propose a method to overcome this problem by performing the surface measurements when the cantilever is vibrating in higher eigenmodes. In this paper we demonstrate the application of active piezoresistive cantilevers operating in this mode. The active piezoresistive cantilever comprises a piezoresistive deflection sensor, a deflection actuator and a nanotip. It is a complete micro-electro-mechanical system, ensuring the highest reliability of cantilever vibration control and detection. Higher eigenmode operations are usually difficult to implement as they usually result in lower deflection and lower sensitivity of the probe vibration deflection. Here we present an experimental modification of the structure of an active piezoresistive cantilever using focused ion beam machining that mitigates both weaknesses. This has enabled the cantilever to scan the surface at a scanning rate of 10 lines s−1 with a maximum speed of 500 μm s−1 and a data acquisition rate of 10 kS s−1, when the probe is vibrating at 380 kHz in the second eigenmode. We also describe a traceable calibration routine (based on analysis of the response of the piezoresistive detector, the output of the HeNe interferometer and precise control of the deflection actuator), together with the cantilever modification process and the development of the measurement setup. We show measurement results of dedicated calibration samples and silicon carbide crystal lattice references.

Multi-objective optimisation of frequency offset and quality factor in semi-conical microwave resonant cavity for syrup brix measurement

Accurate measurement of syrup brix is essential for automated sucrose production because it significantly influences the quality and efficiency of the production process. The microwave resonant cavity method, an effective approach for syrup brix measurement, imposes special performance requirements on the cavity structure design, potentially necessitating unique shapes to capture the properties of the target substance. Traditional empirical design methods for these sensors have significant limitations with nonconventional shapes, often requiring further tuning and analysis of the parameters to adapt to complex geometries and achieve optimal performance. Previous studies have indicated that syrup brix variation can be predicted by the electromagnetic field characteristics of the resonant cavity, specifically the resonant frequency and quality factor, thereby allowing this relationship to be leveraged for sensor optimisation. Therefore, this study presents a systematic multi-objective optimisation approach using electromagnetic simulation software (ANSYS Electronic HFSS) and an Adaptive Reference-based Non-Dominated Sorting Genetic Algorithm (ARNSGA-II), which optimises the frequency offset and quality factor to enhance the sensor sensitivity and accuracy. Experimental comparisons between the optimised and conventional cavity designs demonstrate substantial improvements, with a 60.8% increase in the frequency offset and a 67.2% enhancement in the quality factor. Furthermore, applying the optimised design to a predictive model reduced the mean absolute error to 1.43°Bx, representing a 38.4% improvement compared to the empirical design-based resonant cavity. Results demonstrated that this study provides a robust framework for optimising complex cavity structures and offers valuable insights for the development of high-precision microwave sensors tailored for syrup brix measurements.

A microsystem for in vivo wireless monitoring of plastic biliary stents using magnetoelastic sensors.

With an interest in monitoring the patency of stents that are used to treat strictures in the bile duct, this paper reports the investigation of a wireless sensing system to interrogate a microsensor integrated into the stent. The microsensor is comprised of a 28-μm-thick magnetoelastic foil with 8.25-mm length and 1-mm width. Magnetic biasing is provided by permanent magnets attached to the foil. These elements are incorporated into a customized 3D polymeric package. The system electromagnetically excites the magnetoelastic resonant sensor and measures the resulting signal. Through shifts in resonant frequency and quality factor, the sensor is intended to provide an early indication of sludge accumulation in the stent. This work focuses on challenges associated with sensor miniaturization and placement, wireless range, drive signal feedthrough, and clinical use. A swine specimen in vivo experiment is described. Following endoscopic implantation of the sensor enabled plastic stent into the bile duct, at a range of approximately 17 cm, the signal-to-noise ratio of ~106 was observed with an interrogation time of 336 s. These are the first reported signals from a passive wireless magnetoelastic sensor implanted in a live animal.

Electrodynamic analysis of a sinusoidal antenna for small wave sizes

Background. The work is aimed at developing and researching rigorous methods for calculating thin-wire structures with a complex generatrix shape, having small wave sizes, as well as studying the physical processes occurring in them. A special case of such structures is a sinusoidal antenna operating in a standing current wave mode. Aim. In progress the solution of internal and external problems of electrodynamics is carried out for a sinusoidal antenna of small wave sizes located above an infinitely extended ideal reflector. The currents on the elements of the structure are calculated, its input resistance and radiation characteristics are determined. Methods. The research is based on a strict electrodynamic approach, within the framework of which, for the specified structure in the thin-wire approximation, an integral representation of the electromagnetic field is formed, which, when considered on the surface of conductors together with boundary conditions, is reduced to a system of Fredholm integral equations of the second kind, written relative to unknown current distributions on conductors (internal task). Results. A mathematical model of the radiating structure is proposed, determined: the input resistance of the structure and the basic characteristics of its radiation. It is shown that the operating range of a sinusoidal antenna in the standing wave mode is determined by the quality factor of the input impedance resonances; An increase in the width of the sinusoidal conductor leads to a decrease in the resonant frequencies of the input resistance with a simultaneous increase in the quality factor of the resonances. Conclusion. From a practical point of view, the use of the considered structure allows significantly reduce the dimensions in comparison with a thin electric vibrator, however in this case, the operating range will be correspondingly narrowed, which is determined, due to the weak dependence of the radiation characteristics on frequency, by the quality factor of the resonances. The current distribution on the generatrix of the structure can be considered as a «projection» standing surface wave localized in the plane of a sinusoidal conductor, and resulting from the superposition of forward and backward surface (slow) waves propagating at a speed significantly lower than the speed of light. To further clarify the physics of the processes occurring in the structure, one should use spectral analysis of current functions and study the distributions of the electromagnetic field in the near zone of the structure.

Novel Octa-Structure Metamaterial Architecture for High Q-Factor and High Sensitivity in THz Impedance Spectroscopy.

Terahertz (THz) electric inductive-capacitive (ELC) resonant metamaterials (MMs) are well established tools that can be used to detect the presence of dielectric material (e.g., nanoparticles, bioparticles, etc.) spread on their surfaces within the gap of the capacitive plates of a nanoantenna array. In THz spectroscopy, the amount of the red shift in the resonance frequency (ΔF) plays an important role in the detection of nanoparticles and their concentration. We introduce a new LC resonant MM architecture in the ELC category that maximizes dielectric sensitivity. The newly proposed architecture has an octahedral structure with uniform capacitive gaps at each forty-five-degree interval, making the structure super-symmetric and polarization independent. The inductor core is condensed into a central solid circle connecting all the eight lobes of the octahedron, thereby completing the LC circuit. This ELC resonator has very large active areas (capacitor-gaps), with hotspots at the periphery of each unit cell. The MM structure is repeated in a clustered fashion, so that the peripheral hotspots are also utilized in dielectric sensing. This results in enhancing the quality factor of MM resonance, as well as in increasing ΔF. The research comprises a combination of rigorous system-level simulations along with THz impedance spectroscopy laboratory experiments. We achieved a highly sensitive MM sensor with sensitivity reaching 1600 GHz/RIU. This sensor is fully CMOS compatible and has promising potential applications in high-sensitivity bio-sensing, characterization of nanoparticles, and ultra-low-concentration dielectrics detection, as well as in sensing differential changes in the composition of substances deposited on the metasurface.

Design and Characteristics of Photonic Crystal Resonators for Surface-Emitting Quantum Cascade Lasers

We present our recent development of the surface-emitting quantum cascade laser with a PC (photonic crystal) resonator and a strain-compensated MQW (multiple quantum well) active layer operating at around 4.3 μm. We describe the laser performance mainly from the viewpoint of the design and analysis of the PC resonators, which include both numerical calculations by FEM (finite element method) and analytical calculations using the k·p perturbation theory and group theory. We analyze the resonance quality factor, overlap factor, extraction efficiency, and far-field pattern, and show how the output power and beam quality have been improved by the appropriate design of the PC resonator.

Effect of surface integrity on quality factor of hemispherical resonator

Since hemispherical resonator (HSR) is core component of hemispherical resonator gyro (HRG), the surface integrity directly determines performance parameters of HSR, which then affects the working accuracy and service life of HRG. Therefore, it is necessary to investigate the effect of surface integrity on quality factor of HSR. This work focuses on the surface integrity evolution of fused silica HSR machined by the multi-energy field coupled magnetorheological polishing (MEMRP) and the influence of surface integrity on quality factor. Firstly, the mechanism of removing subsurface damage and surface morphology evolution of the fused silica component machined by MEMRP were investigated to reveal the surface quality evolution rules. It was found that the removal of subsurface damage in fused silica components can be divided into three zones: rapid improvement zone, slow improvement zone, and gentle improvement zone. The improvement of surface roughness is slow in the gentle improvement zone, and the nonlinear regression model between subsurface damage depth and surface roughness is proposed. Then, the surface structure evolution and the mechanical characteristics of the surface layer of fused silica components during the MEMRP process was systematically analyzed. It was found that the initial polishing stage significantly improved the surface mechanical performance parameters. Finally, the quality factor of HSR with various surface qualities was measured. The results show that the subsurface damage depth and quality factor exhibit nonlinear relationship and the crack surface layer has a significant impact on the quality factor. Completely removing the subsurface damage, quality factor of HSR with diameter of 20 mm increased from hundreds of thousands to 2.01×107, and the uniformity of quality factor is 1.2 %. This work could offer theoretical guidance and parameter basis for quickly removing subsurface damage and achieving high-performance manufacturing of fused silica HSR.

Design and analysis of flexible antenna sensor for non-invasive detection of pregnancy in bovine

This research article presents a monopole antenna-based sensor for detecting cow pregnancy through urine analysis. The proposed flexible antenna sensor is printed on denim fabric with a permittivity of 1.7 and a loss tangent of 0.002. The flexible antenna resonates at 2.4 GHz and the gain of the proposed antenna sensor is 2.016 dBi, with a corresponding efficiency of 96.8%. The antenna's dimensions are 30 × 44 × 1 mm3. The substrate region behind the inner area of the radiator ring acts as a sensing area. This substrate can absorb liquids through the sensing area, causing the dielectric properties of the substrate to change according to the dielectric constant of the fluid under test. Urea concentration in pregnant cow urine is 11.06 mg/dL and 1.39 mg/dL in non-pregnant cow urine. The proposed antenna sensor uses microwave signals to detect pregnancy in cows. The deviation in resonance frequency and quality factor are used as key parameters for detecting cow pregnancy.

Versatile Metamaterial: Exploring the Resonances of Symmetry‐Protected Modes for Multitasking Functionality

AbstractIn this work, an experimental study supported by numerical modeling that demonstrates the possibility of exciting Symmetry Protected‐Bound states In the Continuum (SP‐BICs) in a 1D silicon grating fabricated on a lithium niobate substrate is presented. bBoth transverse electric and magnetic polarization states are investigated, leading to the excitation of four quasi‐ Bound states In the Continuum (quasi‐BIC) resonances, exhibiting distinct behaviors. Under standard illumination conditions (plane of incidence perpendicular to the 1D grating lines), two of these resonances are highly sensitive to illumination conditions, while the other two resonances involving unconventional illumination directions (plane of incidence parallel to the grating lines) are more robust to the angle of incidence, but just as sensitive to external stresses in terms of resonance wavelength and quality factor. Additionally, temperature detection is experimentally demonstrated with a Sensitivity of ST = 0.81∼nm °C−1, a state‐of‐the‐art value achieved due to significant electromagnetic field enhancement inside the lithium niobate substrate at the quasi‐BIC resonance. These findings pave the way for their use in various sensing applications (such as biology, electromagnetic, and temperature sensing), as well as nonlinear applications like second harmonic generation, and electro‐ and acousto‐optic modulation.

Development of nanocrystallized magnetoelastic sensors with self-biased effect and improved mass sensitivity

The growing demand for cost-effective and wireless sensing technologies requires the development of simple, efficient and optimized sensors able to accurately detecting external agents. Magnetoelastic resonators represent an alternative to the traditional sensing systems, able to combine all the previously cited factors. Several studies have focused on increasing their sensitivity, in order to make it closer to the market. The present study explores thermal treatments as a novel approach to enhance the sensitivity of magnetoelastic resonators, focusing on the positive impact of crystallization processes induced in magnetoelastic platforms. The experimental results confirm an enhancement of resonant frequency and quality factor of the magnetoelastic platforms as treatment temperature increases. Particularly, the sensor annealed at 550 °C shows an increase of the resonant frequency value of 45 % with respect to the as-quenched platform, being that increase of around 1700 % for the quality factor. In addition, the nanocrystallization induction leads to a self-biased resonance, consequence of the intrinsic magnetization resulting from the crystallization in Fe2B and FeCo phases. Further, the study shows the importance of stability in resonant frequency, emphasizing the potential of the 550 °C-annealed platform for mass sensor applications. Gold deposition experiments reveal the enhanced sensitivity of the sensor annealed at 550 °C of 40 % compared to the as-quenched sensor, as well as an increase of 38 % on its accuracy. These findings represent a significant step forward in the development of magnetoelastic-based mass sensors, highlighting the pivotal role of thermal treatments in optimizing sensitivity for practical and efficient external agents detection systems.

Design optimization of phononic-fluidic resonator systems

Phononic-fluidic resonators utilize an acoustic fluid domain as a defect inside a solid metamaterial lattice, which can be used used to precisely measure acoustic properties of liquids. The design goal is to offer ideal boundary conditions for the acoustic resonator by matching defect resonance with phononic band gap. The design space of metamaterial or phononic crystal and fluidic resonator is nearly unlimited, especially when utilizing fully three-dimensional structures. In this work, we explore numerical shape and topology optimization to focus acoustic energy into the fluid domain and maximize the quality factor of the defect resonance. This requires the use of complex multi-frequency objective functions, while taking into account practical limits such as finite size and losses in the fluid and solid domains. Results highlight notable but limited improvements of quality factor with shape optimization starting from an initial design constrained by the maximum deformation possible. On the other hand, topology optimization results offer unique and unexpected ideas, and thus a deeper dive into the design space.

Deep subwavelength topological edge state in a hyperbolic medium.

Topological photonics offers the opportunity to control light propagation in a way that is robust from fabrication disorders and imperfections. However, experimental demonstrations have remained on the order of the vacuum wavelength. Theoretical proposals have shown topological edge states that can propagate robustly while embracing deep subwavelength confinement that defies diffraction limits. Here we show the experimental proof of these deep subwavelength topological edge states by implementing periodic modulation of hyperbolic phonon polaritons within a van der Waals heterostructure composed of isotopically pure hexagonal boron nitride flakes on patterned gold films. The topological edge state is confined in a subdiffraction volume of 0.021 µm3, which is four orders of magnitude smaller than the free-space excitation wavelength volume used to probe the system, while maintaining the resonance quality factor above 100. This finding can be directly extended to and hybridized with other van der Waals materials to broadened operational frequency ranges, streamline integration of diverse polaritonic materials, and compatibility with electronic and excitonic systems.

A novel microwave microfluidic sensor for purity detection of Medicines’ raw materials

A novel microwave microfluidic sensor is offered for purity detection of medicine’s raw materials which is composed of two radial components and a PDMS microfluidic holder to apply the test samples. The basis of the sensing method is the shift in the resonance frequency and quality factor of the resonator in the presence of liquids with different complex permittivity. To investigate the performance of the proposed sensor, various solvents, binary mixtures of ethanol–water, and raw materials of 3 different medicines have been checked and a 980 MHz variation of resonance frequency, which provided a very high sensitivity equal to 0.53, was achieved for a complex permittivity range of 1–78.4. The proposed sensor has a small size, simple design, easy fabrication process, and very high sensitivity while it is fabricated on an FR4 substrate which decreases the total cost significantly.

Wafer-scale fabrication of InGaP-on-insulator for nonlinear and quantum photonic applications

The development of manufacturable and scalable integrated nonlinear photonic materials is driving key technologies in diverse areas, such as high-speed communications, signal processing, sensing, and quantum information. Here, we demonstrate a nonlinear platform—InGaP-on-insulator—optimized for visible-to-telecommunication wavelength χ(2) nonlinear optical processes. In this work, we detail our 100 mm wafer-scale InGaP-on-insulator fabrication process realized via wafer bonding, optical lithography, and dry-etching techniques. The resulting wafers yield 1000 s of components in each fabrication cycle, with initial designs that include chip-to-fiber couplers, 12.5-cm-long nested spiral waveguides, and arrays of microring resonators with free-spectral ranges spanning 400–900 GHz. We demonstrate intrinsic resonator quality factors as high as 324 000 (440 000) for single-resonance (split-resonance) modes near 1550 nm corresponding to 1.56 dB/cm (1.22 dB/cm) propagation loss. We analyze the loss vs waveguide width and resonator radius to establish the operating regime for optimal 775–1550 nm phase matching. By combining the high χ(2) and χ(3) optical nonlinearity of InGaP with wafer-scale fabrication and low propagation loss, these results open promising possibilities for entangled-photon, multi-photon, and squeezed light generation.

Thin-film dielectric characterization by bound state in the continuum in high contrast grating

Subwavelength high contrast grating (HCG) is renowned for its remarkable ability to produce sharp optical resonance, known as the bound state in the continuum (BIC). Due to the strong surface field enhancement, the resonant wavelength and quality factor (Q factor) are highly sensitive to the dielectric properties of the surrounding medium. We propose utilizing this extraordinary phenomenon for thin-film dielectric characterization based on a film-substrate-grating configuration. By optimizing the geometrical parameters to control the cross-interference between guided modes in the grating and self-interference of propagating wave in the substrate slab, an accidental BIC with a Q factor reaching 104 is excited. Using this BIC, two retrieval methods based on contour mapping of resonant wavelength and Q factor are proposed to extract the complex permittivity (εf) of the film under test. It has been demonstrated that with a film thickness as thin as 10−5 times the grating period, the error in the retrieved Re[εf] is below 2%, and that of Im[εf] is below 10%. The proposed design is a strong candidate for non-destructive dielectric characterization of thin films with thicknesses below one-thousandth of the operating wavelength. This characterization technique can facilitate the development of high-frequency devices for the 6 G high-speed communication.

Research on sensing characteristics of high Q-factor all-dielectric metasurfaces based on geometric breaking

The bound states in the continuum (BIC) are widely used in designing metamaterials with high quality factor (Q-factor) resonances due to their perfect localization in the continuous spectral range coexisting with expanding waves. In this study, a T-shaped nanohole all-dielectric metasurface structure is proposed based on the unique electromagnetic properties of all-dielectric metasurfaces, and the fundamental reason of its coupled state and the theoretical basis of BIC excitation are deeply investigated based on the theory of group theory, and the geometric symmetry is broken from multiple angles, and the coupling relationship between discrete eigenmodes and the external continuum is specifically analyzed during the change of symmetry, its spectral response and near-field distribution are numerically calculated. In addition, based on the modulation mechanism of the incident light polarization angle, the three-channel resonance tuning with two resonances of the same frequency and one of a different frequency is realized under the condition that the resonance position and the Q-factor are not affected. This study not only provides a theoretical basis for the excitation conditions and evolution regularity of symmetry-protected BIC, but also solves the problem in the traditional analysis of resonance phenomena without taking the high Q-factor and stability into account, which can provide new designing methods for optical metasurface devices with multi-channel resonance.