Quality Factor Enhancement Research Articles

Thermal-piezoresistive pumping on double SiC layer resonator for effective quality factor tuning

Active techniques that pump energy into MEMS mechanical resonant devices to improve their performance have attracted great research attention. Herein, we introduce a new concept of bi-layered monolithic silicon carbide resonators utilizing thermal-piezoresistive pumping to boost the quality factor. The device operates based on the electrothermal actuation as a result of a superimposed alternating and direct voltages. The structural stress modulates the electrothermal force generated in the device through the piezoresistive effect. Due to the negative piezoresistive coefficient of the actuator, the mechanical vibration of the structure is fed from the DC bias applied to the structure. The unique design of the double SiC layer allow energy pumped into the system via the thermal-piezoresistive coupling in highly doped SiC nano-film, enabling the enhancement of effective quality factor up to 15.5 %, from 12,200 to 14,100. The change in frequency related to the applied power was measured to be less than 1 % of the designed value. The saturation threshold of the pumping effect was reached at an applied power of 0.18 W. This works provides an avenue to improve the effective quality factor in MEMS bridge structure resonators by the coupling of the thermal-piezoresistive pumping and electrothermal actuation.

Spin-Orbit Interaction of Light Enabled by Negative Coupling in High-Quality-Factor Optical Metasurfaces

We study the negative couplings amid local resonances of photonic metasurfaces and their radiation polarizations. In our analysis, we discover fully circularly polarized, wave-vector variant, radiational eigenstates that are attributed to interorbit coupling-induced negative couplings. Our theoretical model is exemplified via a guided resonance dielectric metasurface that possesses type-II non-Hermitian Dirac points, from where the circular polarization lines emanate. The designed metasurface carries circularly polarized radiation eigenstates in both the zeroth and the first diffraction orders, allowing spin-selective light deflections. The high quality factor and field enhancement of the designed metasurface could lead to applications for spin-selective sensing, beam control, and nonlinear optics. Our findings open a gateway for the design of near-field coupling-assisted metasurfaces.

Enhanced photonics devices based on low temperature plasma-deposited dichlorosilane-based ultra-silicon-rich nitride (Si8N)

Ultra-silicon-rich nitride with refractive indices ~ 3 possesses high nonlinear refractive index—100× higher than stoichiometric silicon nitride and presents absence of two-photon absorption, making it attractive to be used in nonlinear integrated optics at telecommunications wavelengths. Despite its excellent nonlinear properties, ultra-silicon-rich nitride photonics devices reported so far still have fairly low quality factors of sim 6times {10}^{4}, which could be mainly attributed by the material absorption bonds. Here, we report low temperature plasma-deposited dichlorosilane-based ultra-silicon-rich nitride (Si8N) with lower material absorption bonds, and ~ 2.5× higher quality factors compared to ultra-silicon-rich nitride conventionally prepared with silane-based chemistry. This material is found to be highly rich in silicon with refractive indices of ~ 3.12 at telecommunications wavelengths and atomic concentration ratio Si:N of ~ 8:1. The material morphology, surface roughness and binding energies are also investigated. Optically, the material absorption bonds are quantified and show an overall reduction. Ring resonators fabricated exhibit improved intrinsic quality factors sim 1.5times {10}^{5}, ~ 2.5× higher compared to conventional silane-based ultra-silicon-rich nitride films. This enhanced quality factor from plasma-deposited dichlorosilane-based ultra-silicon-rich nitride signifies better photonics device performance using these films. A pathway has been opened up for further improved device performance of ultra-silicon-rich nitride photonics devices at material level tailored by choice of different chemistries.

Integration of an anti-resonant hollow-core fiber with a multimode Yb-doped fiber for high power near-diffraction-limited laser operation.

We proposed and demonstrated mode cleaning in a high-power fiber laser by integrating an anti-resonant hollow-core fiber (AR-HCF) into a multimode laser cavity of an ytterbium (Yb)-doped fiber (YDF). An in-house mode-matched AR-HCF was fusion-spliced to a commercial multimode LMA-YDF, ensuring efficient fundamental mode coupling. The AR-HCF inflicts a high propagation loss selectively on higher-order modes, facilitating fundamental mode operation. Thus, the AR-HCF works as an efficient spatial mode filter embedded in the multimode fiber laser cavity and reinforces preferential amplification of the fundamental mode. Beam quality factor enhancement was achieved from M2 = 2.09 to 1.39 at an output power of 57.7 W (pump-power limited). The beam quality can be further improved by refining the AR-HCF fabrication. The proposed technique has a great potential to be exploited in other multimode fiber laser cavities involving erbium- or thulium-doped fibers and obviates the need for complicated specialty active fiber designs. Compared with the commonly used fiber bending technique, our method can achieve an efficient higher-order mode suppression without inducing mode-field deterioration.

A novel piezoelectric RF-MEMS resonator with enhanced quality factor

This work presents a novel ultra-high frequency Lamb mode Aluminum nitride piezoelectric resonator with enhanced quality factors (Q). With slots introduced in the vicinity of the tether support end, the elastic waves leaking from the tether sidewalls can be reflected, which effectively reduces the anchor loss while retaining size compactness and mechanical robustness. Comprehensive analysis was carried out to provide helpful guidance for obtaining optimal slot designs. For various resonators with frequencies ranging from 630 MHz to 1.97 GHz, promising Q enhancements up to 2 times have all been achieved. The 1.97 GHz resonator implemented excellent f × Q product up to 6.72 × 1012 and low motional resistance down to 340 Ω, which is one of the highest performances among the reported devices. The devices with enhanced Q values as well as compact size possess potential application in advanced radio frequency front end transceivers.

Quality Factor Enhancement of 650 MHz Superconducting Radio-Frequency Cavity for CEPC

Medium-temperature (mid-T) furnace baking was conducted at 650 MHz superconducting radio-frequency (SRF) cavity for circular electron positron collider (CEPC), which enhanced the cavity unloaded quality factor (Q0) significantly. In the vertical test (2.0 K), Q0 of 650 MHz cavity reached 6.4 × 1010 at 30 MV/m, which is remarkably high at this unexplored frequency. Additionally, the cavity quenched at 31.2 MV/m finally. There was no anti-Q-slope behavior after mid-T furnace baking, which is characteristic of 1.3 GHz cavities. The microwave surface resistance (RS) was also studied, which indicated both very low Bardeen–Cooper–Schrieffer (BCS) and residual resistance. The recipe of cavity process in this paper is simplified and easy to duplicate, which may benefit the SRF community.

A Two-Square Shaped Phononic Crystal Strip for Anchor Quality Factor Enhancement in a Length Extensional Mode TPoS Resonator

A Two-Square Shaped Phononic Crystal Strip for Anchor Quality Factor Enhancement in a Length Extensional Mode TPoS Resonator

Manipulating the phonon transport towards reducing thermal conductivity via replacement of Cu by Mn in Cu2SnSe3 thermoelectric system

The substitution of Cu by Mn in the Cu2-xMnxSnSe3 (0 ​≤ ​x ​≤ ​0.20) system is presented with an objective to optimize the thermal transport and analyse thermoelectric behaviour in the low and near room temperature regime (10–350 ​K). The existence of hole-like small polarons as thermally activated carriers, mediating the p-type electrical transport at high temperatures (>80 ​K), is experimentally validated. Temperature dependence of Seebeck coefficient and electrical transport at low temperatures reveals that the variable range hopping (VRH) mechanism is responsible for conduction for temperatures (<80 ​K). Mn doping resulted in the improvement of the Seebeck coefficient, attaining the highest value of 228.3 ​μV/K at 350 ​K for the x ​= ​0.20 sample. A reduction in thermal conductivity is achieved in all the Mn-doped samples, presumably due to strong point defect scattering of high-frequency phonons. The x ​= ​0.20 sample has the lowest thermal conductivity of 1.68 ​W/mK at 350 ​K. Even though the ZT value is observed to decrease with Mn doping, enhancement in thermoelectric quality factor is seen for the sample with x ​= ​0.05, which is attributed to the reduction in lattice thermal conductivity.

A low‐noise current‐reused CMOS active inductor by exploiting G m ‐boosting technique

This work introduces a new low-noise current-reused CMOS active inductor (AI) based on Gyrator-C configuration. In the proposed AI, a simple common-source amplifier is utilised for boosting effective Gm and improving noise performance of the AI. While the Gm-boosting technique improves the noise performance as well as the quality factor of the inductor, a resistor is also added to the feedback path for more quality factor improvement. Rigorous analysis of the proposed circuit shows a significant noise performance and quality factor enhancement. In order to verify the concept and confirm the mathematical analysis, the AI is designed and simulated in a commercial 0.18 μm RF-CMOS technology. The simulation results show that the proposed inductor operates in 1 to 7.2 GHz frequency range, has a 9 nH inductance at 2.864 GHz frequency and 650 μW total power dissipation at 1.8-V supply voltage. Maximum quality factor of 90 is achieved at 2.864 GHz frequency and a quality factor greater than 40 is obtained from 2.4 to 3.3 GHz. The input-referred current noise of the proposed inductor is as low as 22 pA / √ Hz showing 30.5% improvement compared to the conventional AI. The proposed AI is also tunable and sweeping the tuning voltage results in changing extracted inductance from 4.35 to 15.2 nH with only a chip area of 0.003 mm2. Post-layout and different Monte Carlo simulation results also confirm the robust operation of the proposed AI against different process non-idealities.

Ag-Ni bimetallic film on CaF2 prism for high sensitive surface plasmon resonance sensor

Ag-Ni bimetallic film on CaF2 prism for high sensitive surface plasmon resonance sensor

Quality factor enhancement of plasmonic surface lattice resonance by using asymmetric periods

We report that using asymmetric lattice periods can enhance the quality factor of plasmonic surface lattice resonances (SLRs) in two-dimensional array of metal-insulator-metalnanopillars in asymmetric dielectric environment. Simulation results show that by adopting appropriate asymmetric lattice periods, the SLR quality factor can be enhanced by 24\\% compared with the scenario of symmetric periods. We find that the SLR quality factor is optimized when the resonance wavelength is closest to the Rayleigh cutoff wavelength. We also find that the SLRs effect is polarization sensitive in the proposed structure. We expect this work will advance the engineering of SLRs especially in asymmetric dielectric environments, and will promote their applications in sensing.

A large and anisotropic enhancement of the mechanical quality factor in ternary relaxor-PbTiO3 single crystals

Enhancing the mechanical quality factor, Qm, in ferroelectrics is one of the most critical issues for high-power devices, such as therapeutic ultrasonic transducers, large-displacement actuators, and high-frequency transducers. Although previous results have indicated that Qm could be improved through acceptor doping, the mechanism behind this effect is still a mystery, and there have been few reports on the optimization of energy loss in ultrahigh piezoelectric materials such as relaxor-PbTiO3 (PT) single crystals. In this work, we investigate the energy loss associated with various vibration modes in Mn-doped Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT:Mn) single crystals and compare with their undoped PIN–PMN–PT counterpart. We find that Q15, Q24, and Q33 in PIN–PMN–PT:Mn, respectively, undergo 160%, 100%, and 80% enhancements, thus demonstrating very large extrinsic contributions with unusual anisotropies in the Qm enhancement. Such a strong anisotropy is strongly interlinked with the orientation of the internal bias Ei and the charged domain walls. Our results provide some fundamental understanding of domain-engineered ferroelectric materials and materials-by-design for high-performance low-loss devices.

Numerical comparative study on the performance of open photoacoustic cells

An open photoacoustic cell has the merit of not having to frequently disassemble and reassemble to fill up with the gas, compared to the closed counterpart, whereas it has the demerit of causing acoustic radiation losses through the openings. In this paper, we have performed numerical simulations on three different types of open photoacoustic cells, H-type and T-type resonant cells and Helmholtz cell, made by attaching a couple of pipe-shaped extensions to both openings with the intent to lessen the acoustic losses and simultaneously understand the geometrical effect of the opening extensions on their performance. For the numerical study, the perturbed forms of the continuity equation, Navier-Stokes equation, energy equation, and equation of state are solved for the quality factor, acoustic pressure and resonance frequency to evaluate the performance. To predict the acoustic losses through the openings, the computational domain for the measurement of acoustic pressure is extended out of the cells. Results show that the geometrical effect of the opening extensions on the performance varies greatly with the type of open cell. In particular, the H-type open cell is the most desirable choice among the three types because of its high acoustic pressure response and enhanced quality factor. We believe that the results of this study would help us select the right type of open cell required for various practical applications.

Optimization of Inactive Regions of Lithium Niobate Shear Mode Resonator for Quality Factor Enhancement

This work presents the development of a novel process flow for the fabrication of Lithium niobate Lamb wave resonator that allows full control of the shape and size of the released area (undercut) necessary for stabilizing quality factor. We then investigate the influence of the inactive regions of the resonator (i.e. undercut, anchor, bus and gap) on Q; and determine the optimum dimensions for those regions in order to limit the flow of energy escaping from the resonator's body resulting in overall improvement in Q. We report devices with electromechanical coupling ( k <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) of 41% and quality factor ( Q) of 1900 at around 290 MHz resulting in the highest-ever achieved Figure-of-Merit (FoM) of 780 for SH0 mode resonators in X-cut LN. [2020-0363]

Analysis of thermoelastic damping limited quality factor and critical dimensions of circular plate resonators based on axisymmetric and non-axisymmetric vibrations

Thermoelastic damping effects are very important intrinsic losses in microelectromechanical system/nanoelectromechanical system based sensors and filters, which limit the maximum achievable quality factor. Thermoelasticity arises due to coupling between the temperature field and elastic field of the material and its interaction within the material structure. The impacts of axisymmetric and non-axisymmetric vibrations, plate dimensions, material parameters, boundary conditions, mode switching, and temperature on thermoelastic damping limited quality factors (QTED) and critical thickness (hc) were analyzed, and the conditions for an enhanced quality factor were optimized in this work. The analytical models of circular plate resonators have been developed in terms of material performance indices for axisymmetric and non-axisymmetric vibrations. QTED and hc were analyzed based on two boundary conditions: simply supported and clamped–clamped. In order to obtain maximum QTED, micro-circular plates with diamond as the structural material operating at a lower temperature and with non-axisymmetric vibrations are proposed in this paper.

Dual-Band BSF with Enhanced Quality Factor

In the present work, a U-shaped CPW resonator (CPWR) with, generally, unequal arms is proposed to produce high Q-factor bandstop filter (BSF) based on broadside-coupling between the CPWR and a CPW through-line (CPWTL), which are printed on opposite faces of a thin substrate. The unequal arms of the U-shape and the finite width of the ground strips of the CPWR are shown to produce much higher Q-factor than that of equal arms and infinitely extending side ground planes. The dimensions of the CPWTL are optimized for impedance matching while the dimensions of the CPWR are optimized to obtain the highest Q-factor. The effect of the loss tangent of the dielectric substrate material on the Q-factor is investigated. It is shown that the difference between the lengths of the unequal arms of the U-shaped resonator can be used to control the Q-factor. Thanks to the computational efficiency of the employed electromagnetic simulator, enough number of trials has been successfully performed in reasonable time to arrive at the final design of the BSF. A prototype of the proposed BSF is fabricated for experimental investigation of its performance. The experimental measurements show good agreement when compared with the corresponding simulation results.

Nanoelectromechanical Systems: Straining and Tuning Atomic Layer Nanoelectromechanical Resonators via Comb‐Drive MEMS Actuators (Adv. Mater. Technol. 2/2021)

In article number 2000794, Yong Xie, Philip X.-L. Feng, and co-workers demonstrate the additive and heterogeneous integration of 2D nanoelectromechanical systems (NEMS) onto micro actuators made of mainstream silicon-on-insulator (SOI) comb-drive microelectromechanical systems (MEMS), across several orders of magnitude in length scale, thus enabling a chip-scale platform for strain engineering of 2D crystals, and for broad frequency tuning and quality (Q) factor enhancement in atomically thin NEMS resonators.

基于液体透镜的激光多普勒信号品质因子增强技术

基于液体透镜的激光多普勒信号品质因子增强技术

Enhancement of multiferroic characteristics in the Al and Pr co-doped BiFeO3 nanocrystalline

We investigate and enhance the multiferroic characteristics of BiFeO3 by doping Al3+ and Pr3+ cations simultaneously. Bi1-xAlxFe1-xPrxO3 (x=0.00, 0.04, 0.08, 0.12, 0.16) was prepared by sol–gel or auto-combustion method. The structural characterization of the samples was done for Bi1-xAlxFe1-xPrxO3 (x=0.00, 0.04, 0.08, 0.12, 0.16) multiferricnano crystals using X-ray diffraction (XRD), Dielectric properties, and Fourier transform infrared spectroscopy (FTIR). The size of the crystallite was calculated between the range 26.54 and 13.55 nm. We demonstrated the dual cation doping of Fe site by Pr as well as Bi site by Al. Doping of the materials exhibits optimized multiferroic properties. The co-doping of Al3+ and Pr3+ and frequency increases and decreases the dielectric parameters, which is explained by using Wagner theory. This reveals that these particles display resonance phenomenon in the GHz range. Low-frequency AC conductivity defines the grain boundary, while high-frequency dispersion can be ascribed to conductivity grains. Due to rise in the frequency of the applied electric field, real AC electrical conductivity σac increases. FTIR spectra tell us the changes in fundamental vibration absorption bands by the addition of Al3+ and Pr3+ ions. Appreciable enhanced quality factor values proposed the potential use of these materials for energy implementation and in large frequency multiferroic chip indicators. The obtained results proposed a useful contribution of synthesized materials in several technological applications.

High-Q Support Transducer MEMS Resonators Enabled Low-Phase-Noise Oscillators.

Structural and electrode material engineering methodology to attain quality factor enhancement in a support transducer enabled Wine-glass and Lamé mode resonator has been demonstrated in this work. To boost the quality factor, a series of short mechanical couplers is utilized to link the central resonant structure with the piezoelectric transducer arms. Two different top electrode materials are investigated, and the effect of metal loading on the performance of aluminum nitride (AlN)-on-Si-based resonator is investigated in detail. The new resonator design strategy improves the quality factor of the Wine-glass resonator from 9800 to 16 300 while still being able to maintain a spurious-free spectrum for a 200-MHz span, which is crucial for oscillator applications. An optimized oscillation system is realized using a commercially available low-noise amplifier. Careful positioning of the passive components is utilized to attain an ideal operating point for the resonator in the closed-loop condition. Using this scheme, Wine-glass and Lamé mode resonator-based high-performance oscillators with a low phase noise of -133.6 and -132.7dBc/Hz at 1-kHz offset and -153.7 and -150.4 dBc/Hz at 1-MHz offset, respectively, which satisfy that the Global System for Mobile (GSM) communication requirements are attained when normalized to a 13-MHz carrier frequency.