Measured Quality Factor Research Articles

Sonic P-wave attenuation based on fluid pressure differential between joint and matrix

When a P wave compresses in situ rocks saturated with fluid, there is a fluid pressure differential between compliant joints and stiff matrix. The pressure differential automatically drives a mesoscale squirt between joint wall and matrix interior. This mechanism is likely to dominate sonic P-wave attenuation in the field. A new model of P-wave attenuation is established based on mesoscale squirt, in which the first porosity is represented by matrix pores, and the second porosity is represented by joints. The sonic log of a sandstone reservoir in Saudi Arabia is used to illustrate the model. Estimated phase velocity and measured quality factor of sonic P waves are accurately simulated. The results indicate that for the sandstone reservoir, the relative second porosity is 5%, the interjoint distance is 0.1 m, the squirt permeability at very low frequencies is approximately half of the Darcy permeability of the matrix, and the joint gap is 800 μm (quadruple grain diameter of 200 μm). Surprisingly, the model of joint-matrix squirt also is capable of reproducing seismic P-wave attenuation measured in the shallow crust of southern California. Therefore, mesoscale squirt across the joint wall may be the underlying mechanism of attenuation for sonic and seismic P waves shallower than 10 km.

Experimental Realization of Subwavelength Spoof Plasmonic Bound States in the Continuum and Ultra‐Sensitive Detection

AbstractOptical bound states in the continuum (BICs) lies in side the continuum and coexists with extended waves, but it remains perfectly confined without any radiation. This unique property of BICs has led to numerous applications, such as highly surface‐sensitive and spectrally sharp resonances for photonic biosensors. However, it remains challenging to experimentally realize the BICs in a single‐particle system, especially for subwavelength structures. This study presents the existence of optical BICs in a subwavelength metallic microstructure, and quasi‐BICs are observed experimentally in a waveguide system with only a single optimized aluminum meta‐particle. This plasmonic BICs is resulting from the destructive interference of two localized surface plasmon modes. Benefiting from its strong localized field confinement and substrate‐free merit of BICs, the experimentally measured quality factor (Q‐factor) of this transmission dip reach to 273. Additionally, this meta‐particle is experimentally verified to show a good sensitivity for both solids and liquids through the spectral shift of the BICs caused transmission dip. This finding extends the optical BICs to a subwavelength scale and opens practical application opportunities for ultrasmall‐quantity detection of biochemical substances.

Mitigating coherent loss in superconducting circuits using molecular self-assembled monolayers

In planar superconducting circuits, decoherence due to materials imperfections, especially two-level-system (TLS) defects at different interfaces, is a primary hurdle for advancing quantum computing and sensing applications. Traditional methods for mitigating TLS loss, such as etching oxide layers at metal and substrate interfaces, have proven to be inadequate due to the persistent challenge of oxide regrowth. In this work, we introduce a novel approach that employs molecular self-assembled monolayers (SAMs) to chemically bind at different interfaces of superconducting circuits. This technique is specifically tested here on coplanar waveguide (CPW) resonators, in which this method not only impedes oxide regrowth after surface etching but can also tailors the dielectric properties at different resonators interfaces. The deployment of SAMs results in a consistent improvement in the measured quality factors across multiple resonators, surpassing those with only oxide-etched resonators. The efficiency of our approach is supported by microwave measurements of multiple devices conducted at millikelvin temperatures and correlated with detailed X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) characterizations of SAM-passivated resonators. The compatibility of SAMs materials with the established fabrication techniques offers a promising route to improve the performance of superconducting quantum devices.

High Quality Factor Miniaturized CMOS Transmission Lines Using Cascaded T-Networks for 60 GHz Millimeter Wave Applications

This work presents an on-chip 60 GHz lumped element transmission line (TL) using cascaded T-networks with a high Quality factor. Each T-network consists of a series inductance with a shunt capacitance at its center. We have derived the design equations for this TL configuration and proved that a TL whose electrical length ≥ 60° achieves additional miniaturization when implemented with three or more cascaded T-networks. The inductance is implemented using a straight wire model with no ground below it, while the capacitance is implemented using a parallel plate model with a grounding pedestal. Both configurations guarantee maximum inductance per unit length and capacitance per unit area to further improve the miniaturization level. A quarter wavelength TL with three cascaded T-networks is fabricated as proof of concept. The measured and simulated results of the fabricated TL have good agreement, and the measured quality factor is 17 at 60 GHz.

Nonequilibrium quasiparticle distribution in superconducting resonators: Effect of pair-breaking photons

Many superconducting devices rely on the finite gap in the excitation spectrum of a superconductor: thanks to this gap, at temperatures much smaller than the critical one the number of excitations (quasiparticles) that can impact the device’s behavior is exponentially small. Nevertheless, experiments at low temperature usually find a finite, non-negligible density of quasiparticles whose origin has been attributed to various non-equilibrium phenomena. Here, we investigate the role of photons with energy exceeding the pair-breaking threshold 2\Delta2Δ as a possible source for these quasiparticles in superconducting resonators. Modeling the interacting system of quasiparticles, phonons, sub-gap and pair-breaking photons using a kinetic equation approach, we find analytical expressions for the quasiparticles’ density and their energy distribution. Applying our theory to measurements of quality factor as function of temperature and for various readout powers, we find they could be explained by assuming a small number of photons above the pair-breaking threshold. We also show that frequency shift data can give evidence of quasiparticle heating.

The control mechanism of P-wave attenuation in unconsolidated porous media.

Unconsolidated porous media are distinct from consolidated porous rocks in the negligible bulk and shear moduli. This paper is motivated by resolving the control mechanism of P-wave attenuation in the media (represented by Toyoura sands and glass beads) saturated with water. The first model is Biot theory in which longitudinal friction (arising from velocity difference between the two phases) is quantified using dynamic permeability as a function of frequency. The first model simulates phase velocity (Vp) and the ultrasonically measured quality factor (Qp) well. A second model is the transverse squirt model in which squirt is induced by pressure differential between contact of grains (COG) and the main pore space. The second model outputs unrealistic Vp and Qp. The results reveal that P-wave attenuation in unconsolidated porous media (saturated with water) is governed by longitudinal friction rather than intrapore squirt. Remarkably, low-frequency dynamic permeability is much smaller than Darcy permeability, indicating that ultrasonic P-wave is surprisingly capable of indirectly detecting the very narrow gap at COG.

Circle fit optimization for resonator quality factor measurements: Point redistribution for maximal accuracy

The control of material loss mechanisms is playing an increasingly important role for improving coherence times of superconducting quantum devices. Such material losses can be characterized through the measurement of planar superconducting resonators, which reflect losses through the resonance's quality factor Ql. The resonance quality factor consists of both internal (material) losses as well as coupling losses when resonance photons escape back into the measurement circuit. The combined losses are then described as Ql−1=Re{Qc−1}+Qi−1, where Qc and Qi reflect the coupling and internal quality factors of the resonator, respectively. To separate the relative contributions of Qi and Qc to Ql, diameter-correcting circle fits use algebraic or geometric means to fit the resonance signal on the complex plane. However, such circle fits can produce varied results, so to address this issue, we use a combination of simulation and experiment to determine the reliability of a fitting algorithm across a wide range of quality factor values from Qi≪Qc to Qc≪Qi. In addition, we develop a measurement protocol that can not only reduce fitting errors by factors ≳2 but also mitigates the influence of the measurement background on the fit results. This technique can be generalized for other resonance systems beyond superconducting resonators. Published by the American Physical Society 2024

High quality factor metasurfaces for two-dimensional wavefront manipulation

The strong interaction of light with micro- and nanostructures plays a critical role in optical sensing, nonlinear optics, active optical devices, and quantum optics. However, for wavefront shaping, the required local control over light at a subwavelength scale limits this interaction, typically leading to low-quality-factor optical devices. Here, we demonstrate an avenue towards high-quality-factor wavefront shaping in two spatial dimensions based on all-dielectric higher-order Mie-resonant metasurfaces. We design and experimentally realize transmissive band stop filters, beam deflectors and high numerical aperture radial lenses with measured quality factors in the range of 202–1475 at near-infrared wavelengths. The excited optical mode and resulting wavefront control are both local, allowing versatile operation with finite apertures and oblique illumination. Our results represent an improvement in quality factor by nearly two orders of magnitude over previous localized mode designs, and provide a design approach for a new class of compact optical devices.

Resonant Transducers Consisting of Graphene Ribbons with Attached Proof Masses for NEMS Sensors.

The unique mechanical and electrical properties of graphene make it an exciting material for nanoelectromechanical systems (NEMS). NEMS resonators with graphene springs facilitate studies of graphene's fundamental material characteristics and thus enable innovative device concepts for applications such as sensors. Here, we demonstrate resonant transducers with ribbon-springs made of double-layer graphene and proof masses made of silicon and study their nonlinear mechanics at resonance both in air and in vacuum by laser Doppler vibrometry. Surprisingly, we observe spring-stiffening and spring-softening at resonance, depending on the graphene spring designs. The measured quality factors of the resonators in a vacuum are between 150 and 350. These results pave the way for a class of ultraminiaturized nanomechanical sensors such as accelerometers by contributing to the understanding of the dynamics of transducers based on graphene ribbons with an attached proof mass.

Ultrasonic P-wave to determine pore parameters of Spergen limestone

Abstract Ultrasonic waves are capable of helping characterize pores of rocks. A model of viscous squirt is used to simulate phase velocity and the quality factor of ultrasonic P-wave measured in water-saturated Spergen limestone, thus determining pore parameters of the limestone. The measured P-wave had a centroid frequency of ∼0.75 MHz, and two simulations are conducted in this paper. The first simulation yields a dispersion curve with a dipping spike followed by a rising spike. However, it cannot yield the measured quality factor. Another drawback is that one of the pore parameters violates rock physics. The second simulation yields a dispersion curve with a small velocity depression followed by an upward velocity concave; the measured phase velocity and quality factor are simultaneously predicted. The resulting dimensions of the rock unit are 0.3 by 0.333 mm, which is consistent with the mean grain diameter of 0.3 mm. The relative first and second porosities are ascertained to be 0.97 and 0.03, respectively. The aperture distance at contact of grains is inverted as 1.8 µm. Remarkably, the minimum phase velocity of the water-saturated limestone is lower than the Gassmann velocity.

Extending the Linearity of AlScN Contour-Mode Resonators Through Acoustic Metamaterials-Based Reflectors.

This work describes the implementation of acoustic metamaterials (AMs) made of a forest of rods at the sides of a suspended aluminum scandium nitride (AlScN) contour-mode resonator (CMR) to increase its power handling without causing degradations of its electromechanical performance. The increase in usable anchoring perimeter with respect to conventional CMR designs, enabled by the adoption of two AM-based lateral anchors, permits to achieve improved heat conduction from the resonator's active region to the substrate. Furthermore, thanks to such AM-based lateral anchors' unique acoustic dispersion features, the attained increase of anchored perimeter does not cause any degradations of the CMR's electromechanical performance, even leading to a ~15% improvement in the measured quality factor. Finally, we experimentally show that using our AM-based lateral anchors leads to a more linear CMR's electrical response, which is enabled by a 32% reduction of its Duffing nonlinear coefficient with respect to the corresponding value attained by a conventional CMR design that uses fully etched lateral sides.

Robust Ultrahigh‐Q Quasi‐Bound States in the Continuum in Metasurfaces Enabled by Lattice Hybridization

AbstractBound states in the continuum (BICs) have been of growing interest in photonics for their infinite quality factors and strong field localization. The last decade has witnessed great progress on the highest achievable quality factors of quasi‐BICs. However, it remains challenging to realize robust high‐Q quasi‐BICs that are tolerant to the parameter perturbation. Here, it is demonstrated that silicon metasurfaces formed by the hybridization of two lattices can support robust quasi‐BICs with the highest measured quality factor reaching 4130 and the minimum one larger than 1024, even when the relative displacement varies over the whole range of all the possible values. Taking advantage of the two in‐plane mirror‐symmetry points, for the first time, the transition between a toroidal dipole BIC and an electric quadrupole BIC, which guarantees robust ultrahigh‐Q quasi‐BICs at Γ point, is reported. The minimum quality factors of quasi‐BICs can be further improved significantly by shrinking the meta‐atom size and are immune from the intrinsic absorption loss of silicon in the visible regime. It is envisioned that this study will pave the way for achieving robust ultrahigh‐Q metasurfaces and boost their applications in lasing, nonlinear optics, and biosensing.

Characterization of dissipative regions of a N-doped superconducting radio-frequency cavity

We report radio-frequency measurements of quality factors and temperature mapping of a nitrogen doped Nb superconducting RF cavity. Cavity cutouts of hot and cold spots were studied with low temperature scanning tunneling microscopy and spectroscopy, X-ray photoelectron spectroscopy and secondary electron microscopy. Temperature mapping revealed a substantial reduction of the residual resistance upon cooling the cavity with a greater temperature gradient and hysteretic losses at the quench location, pointing to trapped vortices as the dominant source of residual surface resistance. Analysis of the tunneling spectra in the framework of a proximity effect theory shows that hot spots have a reduced pair potential and a wider distribution of the contact resistance between the Nb and the top Nb oxide. Alone, these degraded superconducting properties account for a much weaker excess dissipation as compared with the vortex contribution. Based on the correlation between the quasiparticle density of states and temperature mapping, we suggest that degraded superconducting properties may facilitate vortex nucleation or settling of trapped flux during cooling the cavity through the critical temperature.

Measurement of the cavity-loaded quality factor in superconducting radio-frequency systems with mismatched source impedance

Measurement of the cavity-loaded quality factor in superconducting radio-frequency systems with mismatched source impedance

Wireless Power Transfer System Using High-Quality Factor Superconducting Transmitting Coil for Biomedical Capsule Endoscopy

We experimentally investigated the power transfer efficiency (PTE) of a wireless power transfer (WPT) system for capsule endoscopy that uses a high-temperature superconducting (HTS) transmitting (Tx) coil and a small Cu receiving (Rx) coil. A high-quality factor Tx coil is needed to maximize the PTE of a WPT system. A previously developed high-quality factor coil using double-sided HTS coated conductor wire was used as the Tx coil to improve the PTE. The diameter of the coil was 235 mm. The Rx coil was φ10 × 20 mm. The measured quality factors of the coils were 13,007 and 105, respectively. That of the Tx coil was about 13 times that of a Cu one. We measured the PTE of the WPT system in the facing direction, axial misalignment, and angular misalignment. The measured PTEs of two systems, one with an HTS Tx coil and one with a Cu Tx coil, in the facing direction at a transfer distance of 15 cm were 48.6% and 15.3%, respectively. The PTE of the system with a HTS Tx coil under axial misalignment, and angular misalignment conditions showed sufficiently high robustness compared with a system with a Cu Tx coil. The measured quality factors of the HTS and Cu Tx coils with a liquid phantom were 1,350 and 382, respectively. That of the Tx coil was about 3.5 times that of the Cu one.

Layout of MOS Varactor with Improved Quality Factor for Cross-Coupled Differential Voltage-Controlled Oscillator Applications

In this study, we designed an MOS varactor for application in the differential voltage-controlled oscillator (VCO). To improve the quality factor of the MOS varactor, we proposed a symmetric layout technique of the MOS varactor with reduced parasitic components. Compared with the typical MOS varactor layout, the metal line for the interconnection of the MOS varactors that is inevitable in the typical MOS varactors for the cross-coupled VCO was minimized to reduce the parasitic resistance. In addition, with the reduced interconnection metal line, the overall size of the proposed MOS varactor was also reduced compared with the typical one. To verify the feasibility of the proposed MOS varactor structure, the typical and proposed MOS varactors were designed using a 180 nm RFCMOS process. Compared to the typical MOS varactor, the measured quality factor of the proposed MOS varactor was improved by approximately 32% at the operating frequency of 5.0 GHz. Additionally, we successfully verified that the parasitic capacitance induced by the lossy silicon substrate was reduced in the proposed MOS varactor structure.

High power transmission efficiency of wireless power transfer system using high-quality factor superconducting bulk coil

We developed a high-quality-factor high-temperature superconducting (HTS) bulk coil to increase the power transfer efficiency (PTE) of wireless power transfer (WPT) systems. We proposed the resonant frequency tuning by using the two sapphire substrates thickness of coil support. The configuration of a 65 mm diameter HTS bulk coil was optimized to a resonant frequency of 64 MHz. The measured quality factor of the HTS bulk coil was 9,431, which is 12 times that of the copper coil. At the transfer distance of 20 cm, the measured PTE of the WPT system using HTS bulk coils and one using copper coils were 74.8% and 20.6%, respectively.

Controlling the Modal Confinement in Silicon Nanophotonic Waveguides through Dual‐Metamaterial Engineering

AbstractFlexible control of the modal confinement in silicon photonic waveguides is an appealing feature for many applications, including sensing and hybrid integration of active materials. In most cases, strip waveguides are the preferred solution to maximize the light interaction with the waveguide surroundings. However, the only two degrees of freedom in Si strip waveguides are the width and thickness, resulting in limited flexibility in evanescent field control. Here, a new strategy that exploits metamaterial engineering of the waveguide core and cladding is proposed and demonstrated to control the index contrast in the vertical and horizontal directions, independently. The proposed dual‐material geometry yields a substantially increased calculated bulk sensitivity in the air (0.35 RIU [refractive index unit]/RIU) compared to the best case scenario for a strip waveguide (0.3 RIU/RIU). To experimentally demonstrate the potential of this approach, dual‐metamaterial ring resonators operating with the transverse‐magnetic polarized mode in 220‐nm‐thick waveguides with air as upper‐cladding are implemented. Micro‐ring resonators implemented with strip and dual‐metamaterial waveguides exhibit the same measured quality factors, near 30 000. Having similar measured quality factors and better calculated bulk sensitivity than strip waveguides, the proposed dual‐metamaterial geometry stands as a promising approach to control modal confinement in silicon waveguides.

Quality factor measurement based on direct energy method for piezoelectric resonator

Quality factor measurement based on direct energy method for piezoelectric resonator

Estimating core-mantle boundary temperature from seismic shear velocity and attenuation

The temperature at Earth’s core-mantle boundary (CMB) is a key parameter to understand the dynamics of our planet’s interior. However, it remains poorly known, with current estimate ranging from about 3000 K to 4500 K and more. Here, we introduce a new approach based on joint measurements of seismic shear-wave velocity,VS, and quality factor,QS, in the lowermost mantle. Lateral changes in bothVSandQSabove the CMB provide constraints on lateral temperature anomalies with respect to a reference temperature,Tref, defined as the average temperature in the layer immediately above the CMB. The request that, at a given location, temperature anomalies inferred independently fromVSandQSshould be equal gives a constraint onTref. CorrectingTreffor radial adiabatic and super-adiabatic increases in temperature gives an estimate of the CMB temperature,TCMB. This approach further relies on the fact thatVS-anomalies are affected by the distribution of post-perovskite (pPv) phase. As a result, the inferredTrefis linked to the temperatureTpPvat which the transition from bridgmanite to pPv occurs close to the CMB. A preliminary application toVSandQSmeasured beneath Central America and the Northern Pacific suggest that forTpPv= 3500 K,TCMBlies in the range 3,470–3880 K with a 95% likelihood. Additional measurements in various regions, together with a better knowledge ofTpPv, are however needed to determine a precise value ofTCMBwith our method.