Improved Quality Factor Research Articles

Solid-state MAS NMR at ultra low temperature of hydrated alanine doped with DNP radicals

Magic angle spinning (MAS) nuclear magnetic resonance (NMR) experiments at ultra low temperature (ULT) (≪ 100 K) have demonstrated clear benefits for obtaining large signal sensitivity gain and probing spin dynamics phenomena at ULT. ULT NMR is furthermore a highly promising platform for solid-state dynamic nuclear polarization (DNP). However, ULT NMR is not widely used, given limited availability of such instrumentation from commercial sources. In this paper, we present a comprehensive study of hydrated [U-13C]alanine, a standard bio-solid sample, from the first commercial 14.1 Tesla NMR spectrometer equipped with a closed-cycle helium ULT-MAS system. The closed-cycle helium MAS system provides precise temperature control from 25 K to 100 K and stable MAS from 1.5 kHz to 12 kHz. The 13C CP-MAS NMR of [U-13C]alanine showed 400% signal gain at 28 K compared with at 100 K. The large sensitivity gain results from the Boltzmann factor, radio frequency circuitry quality factor improvement, and the suppression of its methyl group rotation at ULT. We further observed that the addition of organic biradicals widely used for solid-state DNP significantly shortens the 1H T1 spin lattice relaxation time at ULT, without further broadening the 13C spectral linewidth compared to at 90 K. The mechanism of 1H T1 shortening is dominated by the two-electron-one-nucleus triple flip transition underlying the Cross Effect mechanism, widely relied upon to drive solid-state DNP. Our experimental observations suggest that the prospects of MAS NMR and DNP under ULT conditions established with a closed-cycle helium MAS system are bright.

Improving side-pumped solar lasers using ring-array concentrators

ABSTRACT We report here a significant enhancement in side-pumped solar laser collection efficiency and solar-to-laser conversion efficiency by a ring-array primary concentrator. A single and a dual-rod side-pumping configuration were numerically investigated. In the former, a thick laser rod was pumped with the full collection area of the ring-array solar concentrator. In the latter, two thin laser rods were pumped simultaneously. 49.70 W continuous-wave multimode solar laser power, corresponding to 29.06 W/m2 collection efficiency, and 3.06% solar-to-laser power conversion efficiency were numerically attained for the dual-rod side-pumping scheme, being 1.65 and 1.26 times higher than the previous experimental records with Nd:YAG side-pumping configurations. A three-folding-scheme single laser beam technique is presented, enabling a significant improvement of laser beam quality factors.

A Micromachined Resonant Low-Pressure Sensor With High Quality Factor

This article presents a micromachined resonant low-pressure sensor with high quality factor. In this sensor, an island-diaphragm structure was developed, translating low pressures under measurements to frequency shifts of resonators, and improving quality factors of resonators by eliminating modal interferences between resonators and the pressure-sensitive diaphragm. Numerical simulations were conducted, confirming that the developed resonant low-pressure sensor can work properly in the measurement range without modal interference due to the island-diaphragm structure. The fabrication process of the developed resonant low-pressure sensor including key steps of deep reactive ion etching, resonator release and anodic bonding was conducted in this study. Experimental characterization showed high quality factors of resonators (>30000), which were significantly better than previous study (<10000). Moreover, low fitting errors (within ±2 Pa), low hysteresis (within ±2 Pa) and high accuracies (measurement errors within ±2 Pa) were also characterized in the low pressure range of 0.1 kPa-1 kPa and the temperature range of −40 °C–60 °C, validating the high performances of the developed resonant low-pressure sensor.

Guided-mode resonance on pedestal and half-buried high-contrast gratings for biosensing applications

Abstract Optical sensors typically provide compact, fast and precise means of performing quantitative measures for almost any kind of measurand that is usually probed electronically. High-contrast grating (HCG) resonators are known to manifest an extremely sharp and sensitive optical resonance and can constitute a highly suitable sensing platform. In this paper we present two advanced high-contrast grating designs improving the sensing performances of conventional implementations. These configurations, namely pedestal and half-buried HCGs, allow to enhance the shift of the photonic resonance while maintaining the spectral features of the standard configuration. First, the spectral feature of the HCGs was numerically optimized to express the sharpest possible resonance when the structure is immersed in serum. Second, the sensing properties of conventional and advanced HCG implementations were studied by modelling the biological entities to be sensed as a thin dielectric coating layer of increasing thickness. Pedestal HCGs were found to provide a ∼12% improvement in sensitivity and a six-fold improvement in resonance quality factor (Q-factor), while buried HCGs resulted in a ∼58% improvement in sensitivity at the expense of a slightly broader resonance. Such structures may serve as an improved sensitive biosensing platform for near-infrared spectroscopy.

Controlling Microring Resonator Extinction Ratio via Metal‐Halide Perovskite Nonlinearity

AbstractThe exceptionally high optical nonlinearities, wide bandgap, and homogeneity in solution‐processed metal‐halide perovskite media are utilized as optical nonlinear elements on a silicon photonic platform for low‐power‐active components, such as all‐optical switches, modulators, and lasers. With room temperature back‐end‐of‐line compatible processing, a hybrid metal‐halide perovskite (CH3NH3PbI3) microring resonator (MRR) structure is fabricated on a foundry‐processed low‐loss silicon photonic platform. With in‐plane excitation near the light intensity of 110 W m−2, strong two‐photon absorption and free‐carrier absorption saturation are observed. With 103 field enhancements by MRRs, the photorefractive effect in the metal‐halide perovskite reduces linear absorption, represented by 102 improvement of the MRR's intrinsic quality factor and 20 dB enhancement of the extinction ratio.

Ti4+modified MgZrNb2O8microwave dielectric ceramics with an ultra‐high quality factor

AbstractTi4+‐modified MgZrNb2O8(MgZr1‐xTixNb2O8,x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were synthesized using the traditional solid‐state reaction method. Pure MgZr1–xTixNb2O8was detected without any secondary phase via the X‐ray diffraction patterns. According to the sintering behavior and the surface morphology results, the introduction of Ti4+reduced the sintering temperature and promoted the grain growth. The correlations between the dielectric properties and the crystal structure were analyzed through the Rietveld refinement and Raman spectroscopy. The slight shifts of the Raman peaks, corresponding to different vibration modes, were induced by the substitution of Ti4+for Zr4+and related to the improved quality factor. In general, the sample of MgZr0.9Ti0.1Nb2O8 sintered at 1320°C for 4 h exhibited promising microwave dielectric properties with an ultra‐highQ×fvalue of 130 123 GHz (at 7.308 GHz, 20°C), which is potential for 5G communication applications.

Mirror-symmetry breaking mitigates finite-size related performance degradation in guided mode resonance filters

Guided mode resonances in subwavelength patterned thin-films endow them with narrow-linewidth near-unity reflectance peaks. Their ultrathin profile is particularly attractive when mated with image sensor arrays that enables compact field-deployable spectral filtering and sensing systems. While this approach enjoys several advantages over other approaches, a well known limitation is the trade-off between the lateral footprint and spectral linewidth. Mirroring strategies involving metallic or distributed Bragg reflectors have been explored in the past to improve lateral confinement at the expense of increased fabrication complexity, footprint, and insertion loss. Here, we numerically study mirrorless grating modification strategies and predict the mitigation of finite-size related performance degradation. Specifically, we consider mirror symmetry broken miniaturized medium refractive index contrast (silicon nitride) gratings, which exhibit quasi bound states in the continuum (QBIC) resonances. For the same lateral footprint, a nearly 2 fold improvement in quality factor is predicted for the proposed design in comparison to a simple grating surrounded by aluminium mirrors. Numerical study of the design and operational performance of visible-wavelength arrayed filters and multiplexed refractive index sensors is presented. For a typical lateral device footprint of 8 µm, the gratings span wavelengths ranging from 560 nm–800 nm with a coupling efficiency of 43–60%, and a full width half maximum (FWHM) of 4 nm–12 nm. Besides this, the proposed geometry gives a four times better figure of merit (FOM) than the unperturbed medium contrast grating in surface refractometric sensing.

Effects of LBSCA glass addition on sintering behavior, Raman spectroscopy, and microwave dielectric properties of LiNb0.6Ti0.5O3 ceramics

In this study, LiNb0.6Ti0.5O3 (LNT) ceramics with x wt.% (0 ≤ x ≤ 2.0) of added Li2O–B2O3–SiO2–CaO–Al2O3 (LBSCA) glass were prepared by conventional solid-state reaction method. Effects of LBSCA glass on phase composition, microstructure, lattice vibration, and microwave dielectric properties of the LNT-x wt.% LBSCA ceramics were investigated. X-ray diffraction analysis confirmed the formation of single-phase Li1.075Nb0.625Ti0.45O3 in all samples. Combined with Raman spectroscopy, it was suggested that the microwave dielectric properties were highly associated with the bulk density, the vibration damping behavior, the Nb–O bond strength, and the degree of order in crystal structure. Introduction of LBSCA glass resulted in effective decrease in the sintering temperature to 925 °C and contributed to the improvement of quality factor (Q × f) value. The LNT-0.4 wt% LBSCA sample sintered at 925 °C exhibited excellent microwave dielectric properties with ϵr = 62.9, Q × f = 7561 GHz, and τf = 12.56 ppm/°C coupled with good chemical compatibility with silver), which offers good application prospects in the field of low-temperature co-fired ceramic technology.

Compact empty substrate integrated waveguide with high performance and its application in microwave

A compact slow-wave empty substrate integrated waveguide (SW-ESIW) structure is proposed in this article. This structure is composed of an empty substrate with a bottom layer including several rows of internal metallised via holes. In order to decrease both the lateral and longitudinal dimensions, the slow wave effect, caused by physical separation of electric and magnetic fields, is introduced while retaining the advantages of ESIW, such as high quality factor, small insertion loss, and the advantages of SIW, such as low cost and easy processing. Compared to the classical ESIW, the proposed SW-ESIW structure achieves a size reduction of 37% and retains the triple-layer structure. At the same time, in contrast with general SW-SIW structure, which needs double layer with dielectric material, the novel waveguide obtains a significant performance improvement in insertion loss and quality factor. In the article, a fourth-order filter is designed to verify the idea that the SW-ESIW technology provides the low loss, high quality factor and compact structure. By combining the advantages of SW-SIW and ESIW technology, the proposed SW-ESIW structure can be widely applied to the microwave integrated circuits with miniaturisation and high quality factor.

Narrow-band, low-sideband plasmonic filter of asymmetric bi-layer metallic nanoslit arrays.

We propose a narrow-band plasmonic filter with low sidebands in the VIS-NIR regime, consisting of two closely spaced, optically thin layers of asymmetric metallic nanoslit arrays that have equal periods but different slit widths. Based on numerical simulations, we clarify that the filtering characteristics in the transmission spectrum is mainly due to intercoupled local plasmon resonance (LPR) modes in the top- and bottom-layer nanoslits and in-plane waveguiding surface plasmon resonance (SPR) modes bound to the top and bottom metal structure layers respectively. The intercoupled LPR modes boost the transmission in a way that the adjoining nanoslits in the top and bottom metal layers act as optical antennas efficiently receiving and emitting light via intermediate plasmon modes, while the in-plane SPR modes at neighboring wavelengths suppress the transmission, so as to shape the passband peak. It's important that asymmetry of the nanoslits helps to improve quality factor of the intercoupled LPR mode and thus to reduce the passband width. Also, asymmetry of the bi-layer metallic nanoslit arrays helps to suppress the sidebands that are relevant to the higher-order in-plane SPR modes at shorter wavelengths. In the spectrum at longer wavelengths, non-resonant transmission of light is suppressed by increased total thickness of the structured metal layers. Furthermore, a two-dimensional version of the filter structure is presented, demonstrating similar filtering characteristics that can be optimally used for arbitrarily polarized or unpolarized light.

Optimization of the conductivity of microwave components printed by inkjet and aerosol jet on polymeric substrates by IPL and laser sintering

AbstractIn this work, microwave planar resonators are printed with silver nanoparticle inks using two printing technologies, inkjet printing and aerosol jet printing, on polyimide substrates. The microwave resonators used in this paper operate in the frequency band 5–21 GHz. The printing parameters, such as the number of printed layers of silver nanoparticle inks, drop spacing, and sintering time, were optimized to ensure repeatable and conductive test patterns. To improve the electrical conductivity of silver deposits, which are first dried using a hot plate or an oven, two complementary sintering methods are used: intense pulsed light (IPL) and laser sintering. This paper presents the results of different strategies for increasing the final quality factor of printed planar resonators and the trade-offs (sintering time versus final conductivity/unloaded Q) that can be reached. Improvement of the resonator unloaded quality factor (up to +55%) and of the equivalent electrical conductivity (up to 14.94 S/μm) at 14 GHz have been obtained thanks to these nonconventional sintering techniques. The total sintering durations of different combinations of sintering techniques (hot plate, oven, IPL, and laser) range from 960 to 90 min with a final conductivity from 14.94 to 7.1 S/μm at 14 GHz, respectively.

Thermoelastic Damping in Fully Clamped Circular Plate Resonators Based on Nonlocal Thermoelasticity

Thermoelastic damping (TED) is the main source of energy dissipation in resonators. The modelling of TED is of great importance for the design of micro-electro-mechanical systems (MEMS) and the improvement of quality factor. Most of the previous TED models are based on classical continuum mechanics and Fourier heat conductive model. However, small-scale effects are widely found for structures at nano and sub-micron level and the classical theories cannot describe their size-dependent behaviors. Based on the nonlocal elasticity theory and the nonlocal heat conductive model, the thermoelastic coupled governing equations of a circular plate with out-of-plane vibration under the influence of nonlocal effect are derived in this paper. The influences of nonlocal thermoelasticity on TED in circular plates are discussed by numerical examples under different boundary conditions, frequencies, thicknesses and modes.

Quasi-Gaussian Multibeam Solar Laser Station for a Megawatt Solar Furnace

An alternative multirod solar side-pumping concept for the production of multiple quasi-Gaussian beams is proposed. This scheme was based on the One-Megawatt solar furnace in Odeillo, France, which collected and concentrated the solar light into a multilayered pyramidal pumping cavity placed at the focal zone. Each layer was comprised of a square array of four laser heads, each composed of a biconic surface that reflected the solar rays towards a Nd:YAG rod fixed inside a fused silica flow tube. A pyramidal reflector was placed inside the pumping cavity to close it and maximize the harness of solar energy. Compared to the previous multibeam solar laser station design for the same solar furnace, considerable alleviation of thermal lensing effects was achieved with the present approach, allowing the improvement of the laser beam quality factors and, consequently, the possibility of a 32-laser-beam generation, each with a quasi-Gaussian profile. For this case, 9.44 kW total laser power was calculated. Additionally, 20.01 kW total multimode laser power was numerically determined, which corresponds to a 10.93 W/m2 collection efficiency and a 2.0% solar-to-laser power conversion efficiency.

Quasi-Gaussian Multibeam Solar Laser Station for a Megawatt Solar Furnace

An alternative multirod solar side-pumping concept for the production of multiple quasi-Gaussian beams is proposed. This scheme was based on the One-Megawatt solar furnace in Odeillo, France, which collected and concentrated the solar light into a multilayered pyramidal pumping cavity placed at the focal zone. Each layer was comprised of a square array of four laser heads, each composed of a biconic surface that reflected the solar rays towards a Nd:YAG rod fixed inside a fused silica flow tube. A pyramidal reflector was placed inside the pumping cavity to close it and maximize the harness of solar energy. Compared to the previous multibeam solar laser station design for the same solar furnace, considerable alleviation of thermal lensing effects was achieved with the present approach, allowing the improvement of the laser beam quality factors and, consequently, the possibility of a 32-laser-beam generation, each with a quasi-Gaussian profile. For this case, 9.44 kW total laser power was calculated. Additionally, 20.01 kW total multimode laser power was numerically determined, which corresponds to a 10.93 W/m2 collection efficiency and a 2.0% solar-to-laser power conversion efficiency.

Acoustic radiation-free surface phononic crystal resonator for in-liquid low-noise gravimetric detection

Acoustic wave resonators are promising candidates for gravimetric biosensing. However, they generally suffer from strong acoustic radiation in liquid, which limits their quality factor and increases their frequency noise. This article presents an acoustic radiation-free gravimetric biosensor based on a locally resonant surface phononic crystal (SPC) consisting of periodic high aspect ratio electrodes to address the above issue. The acoustic wave generated in the SPC is slower than the sound wave in water, hence it prevents acoustic propagation in the fluid and results in energy confinement near the electrode surface. This energy confinement results in a significant quality factor improvement and reduces frequency noise. The proposed SPC resonator is numerically studied by finite element analysis and experimentally implemented by an electroplating-based fabrication process. Experimental results show that the SPC resonator exhibits an in-liquid quality factor 15 times higher than a conventional Rayleigh wave resonator at a similar operating frequency. The proposed radiation suppression method using SPC can also be applied in other types of acoustic wave resonators. Thus, this method can serve as a general technique for boosting the in-liquid quality factor and sensing performance of many acoustic biosensors.

Improvement of Inductor Performance Parameters With Thin 20 nm Permalloy Patterns

In earlier works, it was shown that the controlled formation of magnetic domains by tailoring shape, size and thickness of Permalloy patterns improves the performance of the inductor compared to bulk thin films. Also, it was shown that 60 nm thick micromagnetic patterns with cross tie walls give better performance compared to 92 nm thick patterns which have asymmetric Bloch walls, owing to larger stray fields. In this work, we compare 20 nm thin film patterns with 60 nm and 92 nm micromagnetic patterns. Experimental results show that inductor embedded with the thinner film i.e. 20 nm permalloy patterns having Neel domain wall provide more improvement in inductance density and quality factor as compared to thicker 60nm having cross-tie domain wall and 92 nm with asymmetric Bloch wall over a broad range of frequencies encompassing the 5G spectrum. There is a 118% peak increment in inductance density and a 204% peak improvement in quality factor in the inductor incorporated with 20 nm thin permalloy patterns.

MOEMS-based accelerometer sensor using photonic crystal for vibration monitoring in an automotive system

Diagnosing the vibration in automobiles is a priority since it provides comfort to the passenger inside vehicle. This paper presents MOEMS accelerometer sensor by using photonic crystal. A spring mass system with photonic crystal technology is visualised and scrutinised. An optical sensing system with photonic crystal technology was studied and simulated with rods in air and holes in slab configuration. The applied force deflection of rectangular defect slab for vertical and horizontal movement is verified. Gaussian pulse propagated through the defect region in a photonic crystal slab resulted in wavelength shift for each defection of slab. Transmission spectrum was obtained for each deflection direction of slab and configurations. Q factor analysed for each displacement of slab found to be 3,210 for HIS vertical movement. It is found that distinct change in wavelength obtained for holes in slab configuration during vertical and horizontal movement of a slab compared to the results of rods in air configuration. High quality factor and sensitivity improvement obtained in this work showed feasibility of future fabrication for HIS and RIA configuration-based MOEMS sensor for vibration monitoring system.

A Neck-down Microsphere Resonator with an Improved Quality Factor of the Whispering-Gallery Mode

A new type of microsphere resonators is designed to improve the quality factor ( $Q$ factor) of the whispering-gallery mode (WGM). The neck-down microsphere was fabricated by tapering and discharging to a single-mode fiber using a commercial fusion splicer. The diameter of the microsphere ranges from 250 $\mu $ m to 330 $\mu $ m, and the stem is from 50 $\mu $ m to 100 $\mu $ m. In addition, the concept of the sphere-to-stem ratio (STSR, the diameter ratio of the sphere to the stem) to evaluate the quality of the resonator is proposed for the first time to our knowledge. The STSR could be adjusted by changing the diameter of the taper waist and the length of the tapered tip. The experimental results show a trend that the larger the sphere-to-stem ratio is, the higher the $Q$ factor is. Using the same interrogating system, we demonstrate that the $Q$ factor of the WGM with a neck-down sphere resonator could reach $1.07\times 10 ^{7}$ , which is 1~2 orders of magnitude higher than that of a normal sphere with a similar size. This method represents a simple and low-cost approach to efficiently increase the $Q$ factor.

Demonstration of nearly pinhole-free epitaxial aluminum thin films by sputter beam epitaxy

Superconducting resonators with high quality factors have been fabricated from aluminum films, suggesting potential applications in quantum computing. Improvement of thin film crystal quality and removal of void and pinhole defects will improve quality factor and functional yield. Epitaxial aluminum films with superb crystallinity, high surface smoothness, and interface sharpness were successfully grown on the c-plane of sapphire using sputter beam epitaxy. This study assesses the effects of varying substrate preparation conditions and growth and prebake temperatures on crystallinity and smoothness. X-ray diffraction and reflectivity measurements yield extensive Laue oscillations and Kiessig thickness fringes for films grown at 200 °C under 15 mTorr Ar, indicating excellent crystallinity and surface smoothness; moreover, an additional substrate preparation procedure which involves (1) a modified substrate cleaning procedure and (2) prebake at 700 °C in 20 mTorr O2 is shown by atomic force microscopy to yield nearly pinhole-free film growth while maintaining epitaxy and high crystal quality. The modified cleaning procedure is environmentally friendly and eliminates the acid etch steps common to conventional sapphire preparation, suggesting potential industrial application both on standard epitaxial and patterned surface sapphire substrates.

Manipulation of fatty acid profiles in roosters’ testes, alteration in sexual hormones, improvements in testicular histology characteristics and elevation sperm quality factor by L-carnitine

The present study was designed to investigate the effects of different levels of l-carnitine (LC) on sperm quality factor (SQF), alterations in testis fatty acid profiles, testicular histology and reproductive hormones in young roosters. Eighteen broiler breeders (Ross 308) weighed at 3 months of age. They were randomly classified while each group had six birds. There were three experimental groups based on the LC concentrations (i.e. LC-0, LC-250, LC-500 mg per kg of diet). After two weeks of adaptation, semen samples were collected and evaluated for seminal attributes every two weeks (from week 24 to week 34). At the end of the experiments, four roosters from each treatment group were sacrificed in order to analyze testicular histology, testis fatty acid profiles and reproductive hormones. Supplementing the diet with two of the LC levels for 22 weeks caused significant rise in sperm concentration, viability and SQF compared to that of the control group (P < 0.05). Quadratic analysis in terms of number of seminiferous tubules and spermatogenesis index were significant (P<0.05). Tubular differentiation index improved linearly by the increasing levels of LC supplementation (P<0.01). The analysis of fatty acid profiles showed that LC significantly (P < 0.05) reduced the percentages of C14:0, C21:0, total saturated fatty acids, total odd-chain fatty acids and n-6/n-3 ratio. Moreover, LC significantly increased the percentage of C20:5n-3 (Eicosapentaenoic acid; EPA) (P < 0.05). Analysis of the correlation coefficient revealed that the SQF is in consistency with EPA (r = 0.98; P < 0.04). In contrast, SQF negatively and significantly correlates with odd-chain fatty acids (r = - 0.99; P < 0.001). The desaturation index for C16 fatty acids (16:1cis/C16:0) negligibly increased linearly as LC was added to the diet (P < 0.05). Furthermore, LC caused the roosters to have significant (P < 0.05) high levels of total testosterone and FSH concentrations. The concentration of LH in different treatment groups, however, turned out to be similar in response to the different levels of LC. In conclusion, long-term supplementation of rooster diet with LC can have beneficial effects on SQF and testis histology. The benefits include alterations in testicular histology, reproductive hormones and testicular fatty acid profiles.