Small Quality Factor Research Articles

Sintering behavior, microstructure and dielectric properties of a novel low loss SrEr2O4 microwave ceramic

In this paper, a novel SrEr2O4 ceramic with relative densities exceeding 96% was synthesized by a conventional solid-state reaction method. Furthermore, investigations of the correlations between its crystal structure, microstructure, and microwave dielectric properties were carried out. Rietveld refinements show that the SrEr2O4 ceramics crystallize in the orthorhombic with the space group Pnam. The SrEr2O4 ceramic sintered at 1575 °C exhibits the good performance of permittivity (εr) = 14.44, quality factor (Q×f) = 23271 GHz, and resonant temperature frequency coefficient (τf) = –21.5 ppm/°C, which is attributed to its high lattice energy, packing fraction, and relative density. In addition, to satisfy the requirement of temperature stability for communication devices, near-zero τf value is obtained by adding CaTiO3 at the cost of a small quality factor loss. The SrEr2O4 + 1.25 wt% CaTiO3 composite exhibits decent properties with εr = 18.57, Q×f = 19940 GHz, and τf = +3.99 ppm/°C, making it an ideal candidate for microwave band applications.

Micro quartz crystal tuning fork based photothermal spectroscopy for trace gas detection

This paper describes a micro-quartz crystal tuning fork (M-QCTF) hermetically sealed in a vacuum environment for the development of low-cost, high-sensitivity photothermal detectors. Compared with conventional QCTF-based photothermal detectors exposed to air, the M-QCTF detector with the approximate stable characteristic resonance frequency (∼32763 Hz) has a small size and high quality factor of 19840. Utilizing the M-QCTF detector and direct absorption spectroscopy (DAS) technology, a gas detection system has been successfully implemented. NO2 was selected as the target gas for evaluating the performance of the M-QCTF based gas sensor. The results indicate a strong linear relationship between the normalized absorbance amplitude of the M-QCTF and the gas concentration, achieving an optimal measurement precision of 117 ppb with an integration time of 230 s. Furthermore, the vacuum packaging structure of the M-QCTF provides advantages such as easy system integration, low cost, and robust anti-interference capability.

A highly sensitive paper-based chipless RFID humidity sensor based on graphene oxide

In this paper, a highly sensitive paper-based humidity sensor is designed and fabricated to overcome the typically low sensitivity and small quality factor of paper-based chipless radio-frequency identification (RFID) humidity sensors. A toroidal inductor-interdigitated electrodes (IDE) capacitor is used as the resonator structure of the new sensor, and the structural parameters of the sensor are optimized using the software of high frequency structure simulator (HFSS) to improve the quality factor. Three paper-based sensor samples were fabricated via screen printing using regular printing paper, Kodak photo paper, and double-sided copper-coated paper as the substrate. In addition, the resonance characteristics, sensitivity, recovery characteristics, stability and other sensor performances were tested. The results show that the sensitivity of the copper-coated-paper-based sensor is significantly better than the two other paper-based sensors. The simulation and test results of the moisture-sensitive characteristics are consistent for graphene oxide (GO) films, which were prepared using the spray method on the surface of the copper-coated-paper-based sensor with mass concentrations of 1 mg/mL, 2 mg/mL, and 5 mg/mL. This indicates that GO films can significantly improve sensor sensitivity when combined with paper-based moisture sensing. Furthermore, the sensitivity increases with increasing GO concentration, the 5 mg/mL GO sensor show a sensitivity of 6.25 MHz/%RH and a range of 60% RH-90% RH. The 1 mg/mL GO humidity sensor shows good recovery characteristics (92.4% recovery). Based on the presence of hydrophilic functional groups in the GO material, a moisture sensing mechanism that GO could improve the sensitivity of the sensor is analyzed.

A qPlus-based scanning probe microscope compatible with optical measurements.

We design and develop a scanning probe microscope (SPM) system based on the qPlus sensor for atomic-scale optical experiments. The microscope operates under ultrahigh vacuum and low temperature (6.2K). In order to obtain high efficiency of light excitation and collection, two front lenses with high numerical apertures (N.A. = 0.38) driven by compact nano-positioners are directly integrated on the scanner head without degrading its mechanical and thermal stability. The electric noise floor of the background current is 5 fA/Hz1/2, and the maximum vibrational noise of the tip height is below 200 fm/Hz1/2. The drift of the tip-sample spacing is smaller than 0.1 pm/min. Such a rigid scanner head yields small background noise (oscillation amplitude of ∼2pm without excitation) and high quality factor (Q factor up to 140 000) for the qPlus sensor. Atomic-resolution imaging and inelastic electron tunneling spectroscopy are obtained under the scanning tunneling microscope mode on the Au(111) surface. The hydrogen-bonding structure of two-dimensional (2D) ice on the Au(111) surface is clearly resolved under the atomic force microscope (AFM) mode with a CO-terminated tip. Finally, the electroluminescence spectrum from a plasmonic AFM tip is demonstrated, which paves the way for future photon-assisted SPM experiments.

Plasmonically Enhanced Superradiance of Broken-Symmetry Diamond Color Center Arrays Inside Core-Shell Nanoresonators.

Superradiance was demonstrated in broken-symmetry arrays of SiV diamond color centers embedded into concave plasmonic nanoresonators. The coupled configurations, including the diamond-silver (bare) and diamond-silver-diamond (coated) nanoresonators’ geometry parameters as well as the emitters’ azimuthal orientation and distance from the metal, were numerically optimized. An objective function consisting of the total fluorescence enhancement multiplied by the corrected emission quantum efficiency was used to design nanoresonators that promote superradiance. A larger total fluorescence enhancement was achieved via a larger number of emitters in both geometries, in coated spherical and in bare ellipsoidal nanoresonators. The superradiance performance was better in the case of a smaller number of emitters in bare spherical and coated ellipsoidal nanoresonators and in the case of a larger number of emitters in coated spherical and bare ellipsoidal nanoresonators. Ellipsoidal geometry is advantageous independent of composition and seeding. The configurations optimal for non-cooperative fluorescence enhancement and superradiance are coincidental. A radiative rate enhancement proportional to the number of emitters was found in wide spectral regions; therefore, superradiance implies N-fold enhancements coexist at excitation and emission. In ellipsoidal nanoresonators, the better superradiance achieved via a smaller quality-factor is accompanied by larger frequency pulling.

Compact triple‐mode bandpass filters based on single perturbed substrate integrated waveguide cavity using coaxial feed

AbstractA compact triple‐mode bandpass filter (BPF) based on a modified rectangular substrate integrated waveguide (SIW) cavity is presented. The perturbation of the dominant mode (TE101) and the third resonance mode (TE102) are realized by two metalized vias in order to keep the first three resonant modes evenly distributed in the passband. Using this strategy, we can control both bandwidth and finite‐transmission zero (FTZ). The bandwidth of BPF can be controlled by simply changing the diameter of the metalized vias. Coaxial excitation is used to achieve a parallel coupling with small external quality factor, resulting in a wideband response. The proposed triple‐mode SIW BPF also has an FTZ, which is decided by the angle between two feeds. In order to verify the proposed strategy, two samples with a center frequency of 5.5 GHz have been designed and manufactured.

Nonvolatile, Reconfigurable and Narrowband Mid-Infrared Filter Based on Surface Lattice Resonance in Phase-Change Ge2Sb2Te5.

We propose a nonvolatile, reconfigurable, and narrowband mid-infrared bandpass filter based on surface lattice resonance in phase-change material GeSbTe. The proposed filter is composed of a two-dimensional gold nanorod array embedded in a thick GeSbTe film. Results show that when GeSbTe transits from the amorphous state to the crystalline state, the narrowband reflection spectrum of the proposed filter is tuned from 3.197 m to 4.795 m, covering the majority of the mid-infrared regime, the peak reflectance decreases from 72.6% to 25.8%, and the corresponding quality factor decreases from 19.6 to 10.3. We show that the spectral tuning range can be adjusted by varying the incidence angle or the lattice period. By properly designing the gold nanorod sizes, we also show that the quality factor can be greatly increased to 70 at the cost of relatively smaller peak reflection efficiencies, and that the peak reflection efficiency can be further increased to 80% at the cost of relatively smaller quality factors. We expect that this work will advance the engineering of GeSbTe-based nonvalatile tunable surface lattice resonances and will promote their applications especially in reconfigurable narrowband filters.

Switched Oscillator With Quarter-Wave, Open-Circuited Stub for Generating Mesoband High-Power Microwave Pulses

This article presents a high-voltage switched oscillator (SO) with a quarter-wave open-circuited stub (OCS) for generating mesoband high-power microwave (HPM) pulses. Unlike the conventional SO, the proposed SO generates mesoband HPM pulses whose dc offset is greatly reduced because the OCS inserted between a charged transmission line and an antenna blocks the flow of the electric energy from a high-voltage power supply to the antenna. Thus, the proposed SO allows the insulation capability of the antenna to be increased and ground-loop-integrated-wideband antennas to be employed. The transient response of the proposed SO is theoretically analyzed to understand its operation mechanism. The results prove that the proposed SO is capable of producing mesoband HPM pulses with a damped rectangular pulse waveform without a high-voltage dc offset. Also, the amplitude and quality factor are discussed. Compared with the conventional SO, the proposed SO has a larger output amplitude and smaller quality factor. Here, the difference between the quality factors is negligible. In addition to the theoretical analysis, we simulated and fabricated the proposed SO. Consequently, the results of the circuit simulation and experiment demonstrated the validity of the proposed design concept.

Anomalies in the switching dynamics of C -type antiferromagnets and antiferromagnetic nanowires

Antiferromagnets (AFMs) are widely believed to be superior than ferromagnets in spintronics because of their high stability due to the vanishingly small stray field. It is thus expected that the order parameter of AFM should always align along the easy-axis of the crystalline anisotropy. In contrast to this conventional wisdom, we find that the AFM order parameter switches away from the easy-axis below a critical anisotropy strength when an AFM is properly tailored into a nano-structure. The switching time first decreases and then increases with the damping. Above the critical anisotropy, the AFM order parameter is stable and precesses under a microwave excitation. However, the absorption peak is not at resonance frequency even for magnetic damping as low as 0.01. To resolve these anomalies, we first ascertain the hidden role of dipolar interaction that reconstructs the energy landscape of the nano-system and propose a model of damped non-linear pendulum to explain the switching behavior. In this framework, the second anomaly appears when an AFM is close to the boundary between underdamped and overdamped phases, where the observed absorption lineshape has small quality factor and thus is not reliable any longer. Our results should be significant to extract the magnetic parameters through resonance techniques.

Optical detection of a subatomic particle with an ultrahigh-resolution carbon sensor

Neutron detection finds wide use in various areas, thus the improvement of the relevant instruments and methods has been focused on for a long time. For the purpose of detecting possible neutrons, in the present paper, we theoretically put forward a carbon nanotube (CNT) sensor based on a single nitrogen-vacancy center coupled to a current-carrying CNT to detect neutrons. With two lasers applied, the accreted mass landing on the nanotube may cause a frequency shift in the probe absorption spectrum. Once the frequency shift is measured, the added mass will be determined. Through the use of this sensor, owing to the small effective mass and high quality factor of the CNT, an ultrahigh mass resolution could be achieved. Due to its ultrahigh resolution, the sensor can be used to detect neutrons. Furthermore, we provide a brand new optical approach for neutron detection.

The characteristics of small field beam quality and output factor of 6 MV FFF

Flattening filter free linear accelerator (FFF LINAC) has been installed in Indonesia. To ensure the accuracy of FFF irradiation, we evaluate the characteristic of FFF in regular and small fields. We employed the Monte Carlo (MC) simulation of FFF LINAC 6 MV as a standard reference in this study. Then, we compared the calculation of FFF beam at central and lateral axis to the measurement and TPS at 10 × 10, 1 × 1, 2 × 2, 3 × 3, 4 × 4 cm2 field sizes. Output factor (OF) and beam quality such that TPR20,10 and penumbra of FFF LINAC were evaluated. TPR20,10(S) for 10 × 10 cm2 was 0.01 differ between MC and measurement whereas it varied from 0.588 to 0.703 for small fields. Dose difference of lateral axis was agreed within 3% except for the penumbra region. Output factor of small fields measurement indicated that field size of 1 × 1 cm2 had a large discrepancy to MC according to this works. The TPR20,10(10) of MC, TPS, and measurement was not a significant difference, while the OF was tending to a large deviation in 1 × 1 cm2. The results showed that our FFF LINAC could be used for small field until 2 × 2 cm2.

Enlarging quality factor in microbeam resonators by topology optimization

The fundamental characteristic of mechanical resonators can be evaluated by resonance eigenfrequency and energy dissipation (or inverse quality factor). Reduced length scales are necessary for achieving high resonance eigenfrequency, which can afford fast response and extraordinary sensitivity to external forces. However, smaller scales will result in higher energy dissipation (or smaller quality factor) in the eigenfrequency of mechanical resonators. A topology optimization process is presented for enlarging quality factor of a microbeam resonator made of linear, isotropic and homogeneous thermoelastic material. The beam’s width is supposed to be considerable so that the plane strain assumption can be satisfied and the design domain is the cross section along the beam’s thickness. By combining the equation of motion and the heat transfer equation, the damping problem of thermoelastic coupling can be solved by a finite-element method. A topology optimization method is used to enlarge quality factor in microbeam resonators. It is found by clamped-clamped and clamped-free microbeam resonators that significant improvements of quality factors can be achieved through this optimization process.

Microcavities with suspended subwavelength structured mirrors.

We investigate the optical properties of microcavities with suspended subwavelength structured mirrors, such as high-contrast gratings or two-dimensional photonic crystals slabs, and focus in particular on the regime in which the microcavity free-spectral range is larger than the width of a Fano resonance of the highly reflecting structured mirror. In this unusual regime, the transmission spectrum of the microcavity essentially consists in a single mode, whose linewidth can be significantly narrower than both the Fano resonance linewidth and the linewidth of an equally short cavity without structured mirror. This generic interference effect-occuring in any Fabry-Perot resonator with a strongly wavelength-dependent mirror-can be exploited for realizing small modevolume and high quality factor microcavities and, if high mechanical quality suspended structured thin films are used, for optomechanics and optical sensing applications.

An underwater parametric array source transducer composed of PZT/thin-polymer composite

The source transducers for parametric array (PA) sound are required to radiate the primary wave with high intensity and directivity so as to generate nonlinear interactions between strong acoustic waves at different frequencies effectively, resulting in so-called PA sound. Thickness-mode piezoelectric transducers using 1–3 lead zirconate titanate (PZT) polymer composites were used to produce wide-bandwidth PA sound due to their ability to generate high-intensity, high-frequency sound beams over a relatively wide frequency band. The small mechanical quality factor of 1–3 PZT polymer composites results in high damping of the polymer matrix leading to a transducer with relatively flat frequency response but yet decreased-power efficiency. A PZT polymer composite that can enhance the power efficiency of a PA source transducer over a wide frequency bandwidth was proposed. This is achieved by adopting thinner polymer matrix layers and PZT rods with dual resonance frequencies. A transducer demonstrated ultrasonic sound up to 197 and 203 dB (re = 1 μP) at 98 and 135 kHz, respectively. The power efficiencies were 50% at 98 kHz and 33% at 135 kHz. PA sound was successfully generated up to 150 dB (re = 1 μP) at 30 kHz with a half-power beam width of 3.4°.

Reducing JPEG False Contour Using Visual Illumination

This paper presents an efficient and simple technique on reducing the false contour problem which often occurs in the JPEG decoded image. The false contour appears on JPEG decoded image while applying small quality factor. This problem induces unpleasant visual appearance. The proposed scheme exploits the usability of Halftoning-Based Block Truncation Coding (HBTC) approach on generating visual illumination to reduce the aforementioned problem. Three HBTC techniques, namely Ordered Dither Block Truncation Coding (ODBTC), Error Diffusion Block Truncation Coding (EDBTC) and Dot Diffused Block Truncation Coding (DDBTC), modify the DC components of all Discrete Cosine Transform (DCT) processed image on JPEG encoding stage. Experimental results show the proposed method superiority on JPEG false contour reduction. To further improve the JPEG decoded image quality, the proposed method utilizes the Gaussian kernel on replacing the DDBTC diffused kernel on spreading the error term. It assumes that the adjacent image blocks have a strong correlation in which high diffused coefficient should be applied on nearest adjacent neighbor. This paper extends the HBTC usability on JPEG false contour suppression.

Effect of Quality Factor on Determining the Optimal Position of a Transmitter in Wireless Power Transfer Using a Relay

In this letter, the optimal placement of a transmitter is investigated under a given arrangement of a relay and a receiver for nonradiative wireless power transfer. Specifically, a closed-form equation is derived for the optimal coupling coefficient between the transmitter and the relay using an equivalent circuit model. Based on this theoretical analysis, it is found that the quality factor of the transmitter has a great effect on determining its optimal placement. In particular, the transmission efficiency can be improved by locating the resonator with a smaller quality factor (e.g., transmitter or receiver) closer to the relay. In order to support the validity of the analysis, the resonators, including the relay, receiver, and three different types of transmitters, are experimentally designed and fabricated. It is shown that our analytical results are well matched with the measured ones in various settings.

Underwater parametric array source transducer composed of PZT rods and thin polymer plate with high power efficiency for wideband sound generation

Nowadays 1-3-type PZT composite transducers are widely used for underwater parametric array (PA) sound source since they can generate highly directional acoustic beam with high intensity, which is the requirements for the PA acoustic phenomenon that results from nonlinearity of a medium. Thanks to the relatively small mechanical quality factor of 1-3 PZT composite, the transducer using it can generate high intensity sounds by relatively low input voltage in the relatively wide frequency band around its resonance frequency. The low mechanical quality factor, however, increase the internal mechanical loss inside the transducer. Consequently, the acoustic radiation efficiency may be lower than expected. In this paper, a dual-resonant-frequency PZT rods are integrated into a thinner polymer plate. Then, the radiation surface increases to enhance radiation power efficiency. The PZT rods with two different lengths, are integrated in the process of molding a polymer plate. The fabricated transducer are operated with the out-of-phase driving method for a dual resonance transducer to generate direct sound beam with a wide frequency bandwidth. The sound pressure levels (SPLs) of the primary waves of the first and second resonant frequencies were 197 dB and 203 dB (re = 1μP), respectively, at 9 m. The acoustic radiation efficiencies at 98 kHz and 135 kHz were 50% and 33%, respectively. The DFW generated by the PA had an SPL of 150 dB (re = 1μP @ 30 kHz) and a high directivity of 3.4° half-power beam width.

Skyrmion-like bubbles and stripes in a thin ferromagnetic film with lattice of antidots

We study the fundamental magnetic states of thin nanostructured (lattice of antidots) ferromagnetic film with quality factor less than unity. It was found that the analog of the skyrmions magnetic bubble lattice could be formed in such ferromagnetic film. These topological excitations are stable and confined due to the antidot lattice, unlike magnetic bubbles in continuous film. Some other magnetic structures similar to those observed in a films with strong uniaxial anisotropy perpendicular to the film plane were also found in the film at different magnitude of external magnetic field. • Magnetic states of film with antidot lattice and small quality factor are discussed. • Skyrmions are found in film with antidot lattice and small quality factor. • Skyrmions are stable and confined due to the antidot lattice.

All-optical switching using Kerr effect in a silica toroid microcavity.

We demonstrate experimentally an all-optical switching operation using the Kerr effect in a silica toroid microcavity. Thanks to the small mode volume and high quality factor of the silica toroid microcavity, we achieved on-chip optical Kerr switching with an input power of 2 mW. This value is the smallest among all previously reported on-chip optical Kerr switches. We also show that this value can be reduced to a few tens of μW by employing a mode with a Q factor of > 2 × 10⁷.

Optimal dielectric and cavity configurations for improving the efficiency of electron paramagnetic resonance probes

An electron paramagnetic resonance (EPR) spectrometer’s lambda efficiency parameter (Λ) is one of the most important parameters that govern its sensitivity. It is studied for an EPR probe consisting of a dielectric resonator (DR) in a cavity (CV). Expressions for Λ are derived in terms of the probe’s individual DR and CV components, Λ1 and Λ2 respectively. Two important cases are considered. In the first, a probe consisting of a CV is improved by incorporating a DR. The sensitivity enhancement depends on the relative rather than the absolute values of the individual components. This renders the analysis general. The optimal configuration occurs when the CV and DR modes are nearly degenerate. This configuration guarantees that the probe can be easily coupled to the microwave bridge while maintaining a large Λ. It is shown that for a lossy CV with a small quality factor Q2, one chooses a DR that has the highest filling factor, η1, regardless of its Λ1 and Q1. On the other hand, if the CV has a large Q2, the optimum DR is the one which has the highest Λ1. This is regardless of its η1 and relative dielectric constant, ɛr. When the quality factors of both the CV and DR are comparable, the lambda efficiency is reduced by a factor of 2. Thus the signal intensity for an unsaturated sample is cut in half. The second case is the design of an optimum shield to house a DR. Besides preventing radiation leakage, it is shown that for a high loss DR, the shield can actually boost Λ above the DR value. This can also be very helpful for relatively low efficiency dielectrics as well as lossy samples, such as polar liquids.