Quality Factor Research Articles

Ultrathin BIC Metasurfaces Based on Ultra-Low-Loss Sb2Se3 Phase-Change Material.

Ultrathin and low-loss phase-change materials (PCMs) are highly valued for their fast and effective phase transitions and applications in reconfigurable photonic chips, metasurfaces, optical modulators, sensors, photonic memories, and neuromorphic computing. However, conventional PCMs mostly suffer from high intrinsic losses in the near-infrared (NIR) region, limiting their potential for high quality factor (Q-factor) resonant metasurfaces. Here we present the design and fabrication of tunable bound states in the continuum (BIC) metasurfaces using the ultra-low-loss PCM Sb2Se3. Our BIC metasurfaces, only 25 nm thick, achieve high modulation depth and broad resonance tuning in the NIR with high Q-factors up to 130. Experimentally, we employ these BIC metasurfaces to modulate photoluminescence in rare earth-doped upconversion nanoparticles, reducing the excitation power for multiphoton photoluminescence and enabling emission polarization manipulation. This work offers a promising platform for developing active resonant metasurfaces, with broad applications including optical modulation, ultrafast switches, color filtering, and optical sensing.

Synthesis and Characterization of the Microwave Dielectric Properties of a (1-x) Li<sub>3</sub>MgNbO<sub>5</sub>–(x) Sr<sub>3</sub>V<sub>2</sub>O<sub>8</sub> Composite for Antenna Application

This study investigates the fabrication of a cylindrical dielectric resonator antenna (CDRA) using ceramic microwave dielectric composites as a resonator. The composites (1-x) Li3MgNbO5-(x) Sr3V2O8 (x=0.25-0.40) have been synthesized via the conventional solid-state reaction method, incorporating 1% B2O3 to lower the sintering temperature. The 0.70-0.30 composite exhibited optimal microwave dielectric properties with a dielectric constant (εr) of 19.20, a quality factor (Q x f) of 3738 GHz, and a temperature coefficient (τf)of -43 ppm/°C. These characteristics render the 0.70-0.30 composite suitable for CDRA applications. The experimentally obtained microwave dielectric parameters were used to simulate the CDRA design using the High-Frequency Structure Simulator design software. A single-feed cylindrical antenna has been fabricated using this composite material as a resonator with a radius × height of 5×6 mm2, mounted on an FR4 substrate measuring close to 25×25×1.6 mm3 and Cu strip as a feed line. The simulated and experimentally measured parameters, including S11, voltage standing wave ratio, and radiation pattern, demonstrated excellent agreement, validating the composite's efficacy for antenna design.

Research on Key Influencing Factors of Ecological Environment Quality in Barcelona Metropolitan Region Based on Remote Sensing

With the rapid development of urbanization, the ecological environment is being degraded. Taking the Barcelona Metropolitan Region as an example, this paper developed an ecological environment quality-assessment system suitable for different times and regions, based on remote sensing, to evaluate the quality of the ecological environment from 2006 to 2018. We also built various ordinary least squares models to analyze multiple variables affecting the ecological environment. Finally, the characteristic triangular spatial structure was used to explain the interaction between the two key variables. The results showed that the ecological quality was unevenly distributed. The largest green space contributed the most benefits but was decreasing and becoming fragmented. NDVI (normalized difference vegetation index) was the most significant natural variable related to the distribution of green space. Precipitation was the most closely related climate factor to NDVI. There was a complex two-way interaction mechanism between the two, and its boundary value was getting higher and higher. In conclusion, the environmental quality of the BMR needs improvement. The characteristic triangle can effectively explain the interaction mechanism between precipitation and NDVI. This study deeply analyzes how various factors affect environmental quality from both the global and internal perspectives and provides a scientific basis for urban ecological management and sustainable development.

Elevating the TMI threshold by incorporating QCW pumping in a high-power CW fiber oscillator

Transverse mode instability (TMI) significantly limits the power scaling of ytterbium-doped fiber lasers. In this Letter, what we believe to be a novel TMI mitigation strategy is proposed and demonstrated in a bidirectional output fiber laser. On the basis of the continuous wave (CW) pump, integrating a quasi-continuous wave (QCW) pump can effectively improve the TMI threshold of the system. In the experiment, a QCW pump with a repetition rate of 1 kHz and a duty cycle of 10% was injected into a CW-pumped fiber laser oscillator, which successfully broke the power limit and alleviated the beam quality degradation. Moreover, when applying a pump modulation depth of approximately 68%, the TMI threshold was notably increased from 624 W in the free-running condition to 1093 W at end B, which is a 469 W (75%) improvement. At this time, the beam quality factor M2 at end B is approximately 1.48, and the stimulated Raman scattering suppression ratio is about 28 dB. Compared to conventional TMI mitigation methods, this approach provides active control in the time domain of fiber lasers, without compromising the optical structures, thereby effectively mitigating TMI and offering broad application prospects.

Excess Intensity Noise in a Nonlinear Amplifying Loop-Mirror-Based Mode-Locked Laser from a Non-Reciprocal Phase Bias

We demonstrate a low-intensity-noise, nonlinear amplifying loop-mirror-based mode-locked fiber laser by optimizing the polarization of the non-reciprocal phase bias and the pump current. If the angle of the waveplate in the non-reciprocal phase bias to the polarization axis of a polarization-maintaining fiber is not carefully aligned, parasitic polarization is induced. The parasitic polarization affects the minimum pump power and dynamic range of pump power for mode-locking, the intensity noise, and the comb power. To reduce intensity noise, the angle of the waveplate for the non-reciprocal phase bias is adjusted, and then the pump power is adjusted. The waveplate angle minimizing the intensity noise maximizes the dynamic range of the pump power for mode-locking and output power. As a result, the relative intensity noise has been suppressed by more than 32 dB at 15 kHz Fourier frequency. The polarization extinction ratio at the non-reciprocal phase bias is critical since it can determine a cavity loss and quality factor of a laser oscillator. Therefore, the additional polarizers cannot improve the intensity noise once the angle is mismatched and the polarization extinction ratio is degraded.

Compact photonic device based on chalcogenide glass loaded lithium niobate on insulator

We propose a hybrid photonic platform based on chalcogenide glass (GeSbSe) integrated with lithium niobate on insulator (LNOI), providing enhanced performance and compactness for integrated photonics. Key photonic components, including grating couplers (GCs), micro-ring resonators, multimode interference (MMI), and the Mach–Zehnder interferometer (MZI), are designed and fabricated on this platform. The micro-ring resonator achieves an intrinsic quality factor of 72,000 and a propagation loss of ∼3 dB/cm. The multimode interference couplers demonstrate minimal excess loss, while the MZI exhibits an extinction ratio exceeding 30 dB over a bandwidth of 50 nm. This hybrid platform, leveraging the unique optical properties of GeSbSe and LNOI, offers scalability and low-loss photonic integrated circuits, with promising applications in high-speed optical communications and signal processing.

Analyze Critical Success Factors in Managing Data Silos to Prevent Poor Data Quality with a Case Study Research Approach

In the context of data silo management in the government sector, Critical Success Factors (CSFs) in data quality are becoming increasingly important, especially for government agencies. Government organizations often face specific challenges in managing data silos in a report due to the complexity of their organizational structure and the large amount of report data that needs to be managed. This research aims to identify, analyze, and understand the relationship between Critical Success Factors (CSFs) in data quality to manage data and prevent data silos in organizations or agencies in report generation using work system theory and provide recommendations for developing strategies to improve data quality in reports. Through a qualitative approach, this research will explore the strategies and practices implemented by government agencies in identifying, preventing, and addressing data silos in reports. For the research methodology, it includes internal surveys with interviews of operators in the government agency. The evaluation results are expected to provide a positive contribution to public services, in the management of report data in the digital era, provide improvements in case of anomalies and deficiencies, and provide a deep understanding related to report generation in a relevant organization or agency.

Analysis of Time–Frequency Characteristics and Influencing Factors of Air Quality Based on Functional Data in Fujian

Increased air pollution is driven by anthropogenic pollution emissions and climate change, which pose great challenges to environmental governance. Strengthening the monitoring of regional air quality levels and analyzing the causes of regional pollution is conducive to the management and sustainable development of the regional atmosphere. Functional data obtained on a wavelet basis were used in the fitting of air quality data of Fujian Province, and wavelet decomposition was performed to obtain low-frequency and high-frequency information. While the Fourier basis cannot adaptively adjust the time–frequency window, resulting in the loss of location information of special frequencies, the wavelet basis solves this problem. Functional analysis of variance was utilized for analyzing spatial differences in air pollution characteristics. Furthermore, the study established a multivariate functional linear regression model to explore the impact of meteorological factors and ozone precursor factors. The results indicated that the overall air quality was gradually improving in Fujian Province, but the concentration of ozone was progressively increasing. Air pollution in coastal areas was higher than that in inland areas. The p-values of the functional analysis of variance for energy values and crest values were less than 0.05. Moreover, the energy entropy and kurtosis values were greater than 0.05. There were significant differences of AQI in the fluctuation amplitude and variation characteristics of different cities. The total squared multiple correlation of regression model was above 50% on average. Ozone is currently the most serious pollution factor, mainly affected by wind speed, temperature, NO2, and CO. In summer, it was principally influenced by VOCs. The findings of this study could act as a reference in exploring the time–frequency characteristics of air quality data and support of air pollution control.

Hydraulic permeability prediction from attenuation in an oil well using the squirt flow model

A practical methodology is presented for estimating the hydraulic permeability from the wave attenuation at sonic frequencies using the poroelastic squirt flow model associated with the mechanism that encompasses the interaction between solid and fluid in an oil well. The methodology consists of four stages: a) the petrophysical evaluation, b) the static rock physics modeling that includes its diagnostics, c) the estimation of wave attenuations using an inversion scheme to optimize the Z critical parameter from the squirt flow model, d) the correlation between attenuations and the Z parameter with hydraulic permeabilities obtained by conventional well logs and available core analysis. The correlations are the means to establish the predicted hydraulic permeabilities from sonic and ultrasonic data. The obtained results suggest that the Z parameter is low while attenuations are high when the medium presents high porosity and permeability. In the methodology, the inversion scheme is proposed to find the Z parameter, the velocity dispersion, and attenuations in terms of the inverse quality factors, respectively for P-wave (QP –1) and S-wave S (QS –1) using a simulated annealing technique. The results from the application of the methodology are validated with core data (water saturation, porosity, and permeability) and mineralogical analysis from thin sections by the point counting technique. This methodology promises a means for predicting the hydraulic permeability from sonic and ultrasonic velocities in a well.

SPECTRAL and SOURCE PARAMETERS of NORTH CAUCASUS EARTHQUAKES in 2020

The spectral parameters of the sources of 38 earthquakes in the North Caucasus were determined from the displacement spectra of S-waves for the period 2020. The calculations used events with an energy classes KR=9.3–12.9 and waveforms from stations with epicentral distances 50–250 km. The values of local magnitudes ML were calculated using a new calibration curve. The calculation of source spectra was carried out in the SEISAN program based on the frequency-dependent quality factor Q(f). The following values were obtained: 0 – spectral density, f0 – corner frequency, M0 – scalar seismic moment, Mw – moment magnitude,  – stress drop, and RMS for each of the parameters. For 30 earthquakes with KR=9.0–12.9 focal mechanisms were calculated, which are represented by reverse faults (including reverse faults with strike-slip components – 73 %), normal faults – 20 % and strike-slip – 7 %, which corresponds to deformation processes in the collision zone of the Arabian and Eurasian plates.

Nonlinear piezoelectric quartz MEMS resonator with electrically tunable stability for enhanced performance of resonant accelerometer

Piezoelectric quartz resonators are attracting increasing attention in resonant accelerometers due to their excellent quality factor and stable crystal structure, which helps to achieve more robust mechanical sensing. Previously quartz resonators operated in the linear region of an atmospheric pressure environment. To achieve a better signal-to-noise ratio, it is imperative to investigate the effect of nonlinear effects on the performance of quartz resonators. In this work, piezoelectric quartz resonators' nonlinear dynamics are researched, and frequency bifurcation and phase stretching phenomena are systematically characterized. We show the effect of the quality factor and temperature on the bifurcation point and reveal the modulation mechanism of the resonator operating point on stability. We find a method to rapidly change the stability and bandwidth of the resonator by conveniently tuning the electrical parameters and validate it in static and dynamic experiments on a quartz resonant accelerometer, which can be used in resonant sensors and actuators.

Direct laser micro-drilling of high-quality photonic nanojet achieved by optical fiber probe with microcone-shaped tip

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.

Fano resonance and exceptional point enhanced sensing in a grating coupled heterostructure

Fano resonance line shape performs ultrasensitive sensing characteristics as its ultrahigh quality factor. Here, we theoretically investigate the sensitivity and figure of merit (FOM) of a novel, to our knowledge, multilayered heterostructure as a sensor. The heterostructure is non-Hermitian and composed of one layer of gold grating, multilayer polyethylene, and polymethyl methacrylate. The rigorous coupled wave analysis method (RCWA) is used to investigate the reflection characteristics of the structure. Interference between the “dark mode,” excited by the grating, and the “bright mode,” excited by the central layers, produces Fano resonance in the forward reflection spectra. Adjustment on the structure parameters can reduce the valley value of the Fano peak to zero, giving rise to scattering exceptional points (EPs). At the wavelength of the EP, the ambient temperature and mechanical stress fluctuations will lift the reflection, available for sensing signal. The sensitivity is higher than that of the structure without Fano peaks and EPs. Moreover, we use the spectral shift for refractive index sensing with a FOM exceeding 200RIU−1.

Reproductive performance of Channa striata in wetland ecosystems: a fuzzy logic approach to water quality and eco-climatic factors for long-term sustainable management and aquaculture advancement.

The striped snakehead, Channa striata, is commercially and nutritionally important due to its medicinal properties, such as wound healing and antimicrobial abilities. This study investigated the reproductive biology of C. striata in relation to hydro-climatic changes using a fuzzy logic approach for long-term management in the wetland ecosystem (Gajner beel), Bangladesh. A total of 1200 C. striata individuals were collected monthly during January to December 2019 using various fishing methods. Measurements of total length (TL), body weight (BW), and gonad weight (GW) were taken with a precision of 0.01cm and 0.01g, respectively. The GSI (gonadosomatic index in %), MGSI (modified gonadosomatic index in %), and DI (Dobriyal index) were used to determine size at sexual maturity (Lm) and the spawning season. Results revealed a wide range of TL, ranging from 12.7 to 46cm. The Lm was estimated between 21.7 and 25.33cm based on various model as TL vs. GSI, MGSI, and DI; TL-fork length (FL) regressions; and maximum length (Lmax) for this species. The spawning period was observed from April to July, peaking in May, indicated by higher GSI, MGSI, and DI values. Eco-climatic factors showed a significant relationship with GSI, except for total dissolved solids (TDS). Rising temperatures and declining rainfall could delay spawning of C. striata. A fuzzy logic approach was employed to predict future GSI changes over extended periods (e.g., 50 or 60years), enabling anticipation of shifts in the timing and duration of the spawning season. Finally, the findings of our research might be effective to carry out specific conservation efforts of C. striata in response to climate variability in sub-tropical water.

Publisher's note: “High quality factor of bound states in continuum in hBN metasurface” [J. Appl. Phys. 136, 133103 (2024)

Publisher's note: “High quality factor of bound states in continuum in hBN metasurface” [J. Appl. Phys. 136, 133103 (2024)

Single-Frequency Birdcage Coils for Deep Tissue Perfluorocarbon Magnetic Resonance Imaging in Mice.

Fluorine-19 (19F) MRI has become an established tool for invivo cell tracking following exvivo or invivo labelling of various cell types with 19F perfluorocarbons (PFCs). Here, we developed and evaluated novel mouse-specific radiofrequency (RF) hardware for improved dual 1H anatomical imaging and deep tissue 19F MR detection of PFCs. Three linearly polarized birdcage RF coils were constructed-a dual-frequency 1H/19F coil, and a pair of single-frequency 1H and 19F coils, designed to be used sequentially. RF coil quality factors (Q values), signal homogeneity and sensitivity were benchmarked against a commercially constructed dual-frequency 1H/19F surface coil. RF homogeneity was assessed using a phantom designed to mimic PFC localization at depth in a mouse. The single-frequency birdcage coils (1H and 19F) displayed more uniform coverage and enhanced signal-to-noise ratios (SNRs) compared to both the birdcage and surface dual-frequency coils for 19F detection. Bilateral injection of a perfluoropolyether nanoemulsion into the footpads of female athymic nude mice, resulting in drainage to various lymph nodes and subsequent accumulation in lymph node macrophages, provided a platform to assess differences in SNRs and contrast-to-noise ratios (CNR) between both coil configurations as a function of depth and location. The single-frequency 1H coil provided significantly increased CNR in anatomical images (p < 0.001) with increased anatomical coverage compared to the dual-frequency surface coil. The single-frequency 19F birdcage coil offered increased PFC detectability with significantly higher SNR in renal, lumbar, sciatic and popliteal lymph nodes (p < 0.01) compared to the dual-frequency surface coil. Interestingly, the percentage difference between SNR measurements in lymph nodes between the single-frequency 19F coil and the 1H/19F surface coil had a linear relationship with increasing distance from the surface coil (R2 = 0.6352; p < 0.0001), indicating a potential disagreement for imaging experiments that rely on 19F spin quantification at increasing depth within the mouse using surface RF coils.

Sustainable Fabrication and Transfer of High-Precision Nanoparticle Arrays Using Recyclable Chemical Pattern Templates.

Nanoparticle (NP) arrays, particularly those with plasmonic properties, have diverse applications in electronics, photonics, catalysis, and biosensing, but their precise and scalable fabrication remains challenging. In this work, a facile chemical-based strategy is presented for the fabrication of precise NP patterns using a combination of soft thermal nanoimprinting and template-directed assembly. The approach enables the creation of well-defined NP arrays with single-particle resolution and yields over 99%, covering a diverse range of NP sizes from 30 to 150nm. These patterns can be transferred onto various substrates including semiconductors, insulators, 2D materials, and flexible polymers, maintaining high uniformity and repeatability for over 60 cycles with minimal degradation. Moreover, the method enables the fabrication of extensive NP arrays up to 1 cm2 with a positional accuracy of ±11 nm for 30nm NPs. As a result, the obtained silver NP arrays exhibit ultranarrow surface lattice resonances with a linewidth of 4nm and a quality factor (Q) of 216. The method offers new avenues for the creation of plasmonic NP arrays for flexible and wearable devices.

Revisiting Passengers’ Perceptions of Airline Service Quality: A Theory-Driven Machine Learning Approach Using Big Data

ABSTRACT Understanding the discrepancy between passenger expectations and airline offerings is critical for improving service quality and customer satisfaction. This study expands the current knowledge regarding airline service quality dimensions by investigating actual passenger experiences. Analyzing 1,389,689 online reviews from TripAdvisor.com, structural topic modeling identified 29 airline service quality factors. Drawing upon AIRQUAL and SERVQUAL as theoretical frameworks, five unique dimensions emerged: flight attendance service, flight schedule, in-flight entertainment, in-flight meal, and baggage. Moreover, regression analysis highlights the significance of flight attendant services and hidden critical factors, such as attention to child passengers and special requests, in enhancing customer satisfaction. This study provides theoretical implications by uncovering airline service quality factors recognized by passengers and suggesting five potential service quality dimensions suitable for the airline context. Practically, the current study guides airline managers in understanding a passenger viewpoint and avoiding the service gap by combining machine learning, econometric approaches, and existing theories.

Impact of the Quality of Financial and Banking Applications Used on Smartphone on the Customer Satisfaction of Jordanian Islamic Bank

This study aimed to identify the impact of the quality of financial and banking applications through the dimensions of (information security, trust, privacy) used on smartphones on the satisfaction of Jordanian Islamic bank customers. The researcher employed a descriptive-analytical approach in constructing the study. The study population consisted of all customers of Jordanian Islamic banks. The researcher developed a research tool (a questionnaire) to align with the study’s dimensions. A random sample of Islamic bank customers was selected, and the research tool was distributed to them electronically. The researcher was able to obtain responses from 249 participants. One of the key findings of the study was that there is a high level of usage of financial and banking applications on smartphones in Islamic banks. Among the dimensions, “privacy” ranked the highest in importance based on the participants’ responses. The results also revealed a significant impact of the quality of financial and banking applications used on smartphones, through the dimensions of (information security, trust, and privacy), at a significance level of (α ≤ 0.05) on the satisfaction of Jordanian Islamic bank customers. Among the key recommendations was the need for greater focus on quality factors related to financial and banking applications by emphasizing the dimensions of information security, trust, privacy, and data protection due to their significant role and impact on customers using these applications. Additionally, there is a potential for further research and studies on the factors affecting the quality of financial and banking applications on smartphones for electronic banking services offered to customers.

Thickness dependence of the mechanical properties of piezoelectric high-Q_m nanomechanical resonators made from aluminium nitride

Abstract Nanomechanical resonators with high quality factors (Qm) enable mechanics-based quantum technologies, in particular quantum sensing and quantum transduction. High-Qm nanomechanical resonators in the kHz to MHz frequency range can be realized in tensile-strained thin films that allow the use of dissipation dilution techniques to drastically increase Qm. In our work, we study the material properties of tensile-strained piezoelectric films made from aluminium nitride (AlN). We characterize crystalline AlN films with a thickness ranging from 45nm to 295nm, which are directly grown on Si(111) by metal-organic vapour-phase epitaxy. &amp;#xD;We report on the crystal quality and surface roughness, the piezoelectric response, and the residual and released stress of the AlN thin films. Importantly, we determine the intrinsic quality factor of the films at room temperature in high vacuum. We fabricate and characterize AlN nanomechanical resonators that exploit dissipation dilution to enhance the intrinsic quality factor by utilizing the tensile strain in the film. We find that AlN nanomechanical resonators below 200nm thickness exhibit the highest Qf-product, on the order of 1012Hz. We discuss possible strategies to optimize the material growth that should lead to devices that reach even higher Qf-products. This will pave the way for future advancements of optoelectromechanical quantum devices made from tensile-strained piezoelectric AlN.