Resonance Frequency Of Cavity Research Articles

Switchable SAW Resonators and Ladder Filters Composed of Interdigitated Combs.

This work presents the development of switchable surface acoustic wave (SAW) resonators fabricated on a LiNbO3 substrate, which uses the electrical Bragg bandgap concept to control the resonance frequency. The modification of the electrical condition of electrode arrays shifts their bandgap center frequency, which in turn changes the effective cavity length and resonance frequency of the resonator. This method uses the electrodes already present in SAW devices, thus reducing the complexity of potentially tunable SAW components. In this article, the electrodes that make up the cavity mirrors are connected into interdigitated comb pairs (IDCPs), reducing the necessary number of switches for operation. Finite-element method (FEM) simulations are used to analyze resonator operation and design difficulties are discussed. Frozen (with no possibility of switching) and switchable versions of a chosen resonator structure are fabricated to experimentally showcase resonator operation. It is found that it is possible to design switchable SAW resonators, which require a single switch and present a relative frequency jump of around 2.3%. Finally, frozen single-cell and four-cell ladder filters are fabricated as a proof of concept of a switchable SAW filter.

Finite element analysis of a Helmholtz transducer jointly driven by a trilaminar ring and a piezoelectric circular tube

Abstract Crosswell seismic survey can image the crosswell geological anomalies with high resolution in 3D. To effectively conduct crosswell seismic survey, it is necessary to use a seismic source capable of transmitting low-frequency and high-power signals in a compact size. In this paper, a novel Helmholtz transducer is proposed, which utilizes both the bending vibrations of the trilaminar ring and the radial vibrations of the piezoelectric circular tube to simultaneously drive the vibration of the Helmholtz liquid cavity. This design reduces the resonant frequency of the liquid cavity while enhancing the transmitting voltage response at the liquid cavity resonant frequency. The influence of the inner radius of the trilaminar ring, the outer radius of the ceramic ring and the length of the piezoelectric circular tube on the liquid cavity resonant frequency and the transmitting voltage response at the liquid cavity resonant frequency is simulated using the finite element method. The simulation results provide a theoretical foundation for optimizing the design of such transducers.

Polariton creation in coupled cavity arrays with spectrally disordered emitters

Integrated photonics has been a promising platform for analog quantum simulation of condensed matter phenomena in strongly correlated systems. To that end, we explore the implementation of all-photonic quantum simulators in coupled cavity arrays with integrated ensembles of spectrally disordered emitters. Our model is reflective of color center ensembles integrated into photonic crystal cavity arrays. Using the Quantum Master equation and the Effective Hamiltonian approaches, we study energy band formation and wavefunction properties in the open quantum Tavis–Cummings–Hubbard framework. We find conditions for polariton creation and (de)localization under experimentally relevant values of disorder in emitter frequencies, cavity resonance frequencies, and emitter-cavity coupling rates. To quantify these properties, we introduce two metrics, the polaritonic and nodal participation ratios, that characterize the light-matter hybridization and the node delocalization of the wavefunction, respectively. These new metrics combined with the Effective Hamiltonian approach prove to be a powerful toolbox for cavity quantum electrodynamical engineering of solid-state systems.

Dynamic Fabry-Pérot cavity stabilization technique for atom-cavity experiments

We present a stabilization technique developed to lock and dynamically tune the resonant frequency of a moderate finesse Fabry-Pérot (FP) cavity used in precision atom-cavity quantum electrodynamics (QED) experiments. Most experimental setups with active stabilization either operate at one fixed resonant frequency or use transfer cavities to achieve the ability to tune the resonant frequency of the cavity. In this work, we present a simple and cost-effective solution to actively stabilize an optical cavity while achieving a dynamic tuning range of over 100 MHz with a precision under 1 MHz. Our unique scheme uses a reference laser locked to an electro-optic modulator (EOM) shifted saturation absorption spectroscopy (SAS) signal. The cavity is locked to the PDH error signal obtained from the dip in the reflected intensity of this reference laser. Our setup provides the feature to efficiently tune the resonant frequency of the cavity by only changing the EOM drive without unlocking and re-locking either the reference laser or the cavity. We present measurements of precision control of the resonant cavity frequency and vacuum Rabi splitting (VRS) to quantify the stability achieved and hence show that this technique is suitable for a variety of cavity QED experiments.

Frequency reduction and attenuation of the tire air cavity mode due to a porous lining

The tire air cavity mode is known to be a significant source of vehicle structure- borne road noise near 200 Hz for current generation passenger vehicles, and a porous lining placed on the inner surface of a tire has proven to be an effective countermeasure. The two noticeable effects of such a lining are the reduction in the cavity resonance frequency and the attenuation of the air cavity mode. In the present work, through both theoretical and numerical analysis, the mechanisms underlying the effects of a porous lining were studied. A two-dimensional duct-shaped theoretical model and a two-dimensional torus-shaped numerical model were created to investigate the lined tire in conjunction with the Johnson- Champoux-Allard model describing the viscous and thermal dissipative effects of the porous material. The design parameters of the porous lining were varied to study their impact and to identify optimal ranges of the design parameters, in particular, the flow resistivity. Finally, in an experimental analysis, the sound attenuation and the frequency drop were observed in measurements of force, acceleration, and sound pressure. In conclusion, it was demonstrated that the suggested theoretical and numerical models successfully predict the effects of porous linings and that the frequency reduction results from the decreased sound speed within the tire owing to the presence of the liner.

Self-induced back-action for aperture trapping: Bethe-Rayleigh theory.

A dielectric (nano)particle can influence the local electromagnetic field and thereby alter its interaction with that field through the process of self-induced back-action. While this phenomenon is usually considered theoretically as a change in a cavity resonance frequency, such theoretical approaches are not as appropriate when considering systems away from resonance, such as with a subwavelength aperture in a metal film. Here we consider the interaction between an aperture, modelled with Bethe theory as a magnetic dipole, and a Rayleigh particle, modelled as an electric dipole. Using this magnetic dipole - electric dipole interaction, we quantify the self-induced back-action of the particle on the aperture transmission and the optical trapping potential. The model shows quantitative agreement with finite-difference time-domain simulations. This shows that the physics of self-induced back-action for an aperture and a nanoparticle can be understood in terms of dipole-dipole coupling.

The resonance mode splitting rule of the rotating tire cavity considering the vertical load

According to the modal splitting theory of the tire cavity at different rotation speeds and the modal splitting theory of the tire cavity under different loads, the expression of the resonance frequency of the tire cavity of the rotating tire under load conditions is proposed. Based on the elastic contact theory, the characteristic geometric parameters of grounded tires are obtained. The resonance frequency of the tire cavity is predicted by using the common rule of the characteristic geometric parameters of grounded tires and the characteristic section parameters of the tire cavity, to further clarify the basic rule of changes of vibration mode shapes accompanied by the resonance mode splitting of the tire cavity.

Experimental study of applying plant-derived materials to sound-absorbing structures for cabin noise reduction of electric vehicles

Electric vehicles generate different interior noise than internal combustion engine vehicles at low speeds. To investigate the cause of the interior noise of electric vehicles at low speeds (30 km/h) and to reduce the noise, a Helmholtz resonator made of molded pulp, a material derived from plants, is fabricated, and its noise reduction effect is experimentally evaluated. First, a molded pulp Helmholtz resonator is fabricated and tested with an impedance tube. Then, this Helmholtz resonator is installed inside the tire and can reduce the cavity resonance noise. Then, driving tests are conducted on an electric vehicle with tires equipped with this molded pulp, and it is possible to reduce the sound pressure at the ear position at the frequency of the tire cavity resonance. Finally, driving tests are conducted with standard tires, and this molded pulp in the cabin reduces the noise at the tire cavity resonance frequency. From this, at low speeds (30 km/h), we can demonstrate that tire cavity resonance is the source of noise in an electric vehicle's cabin and that it is possible to reduce tire cavity resonance without directly installing Helmholtz resonator in the tires.

Modulation instability in a microresonator with graphene saturable absorber, frequency selective feedback and external potential

Modulation Instability is studied in the presence of an external periodic potential in microresonator comprising of a vertical cavity surface emitting laser with saturable absorber and frequency selective feedback. The role of intensity of input field, pump parameter, diffraction coefficient and saturable absorption on the modulation instability has been investigated. Thus, Modulation instability can be tuned by varying the system parameters. This aspect would be beneficial for the purpose of encryption. It is also observed that modulation instability is not explicitly dependent on externally applied potential whereas the effect of potential is shown implicitly by using numerical analysis. The presence of an external potential give the operating range of resonance frequency of the optical cavity instead of one value at the same system parameters. This operating range of resonance frequency is spatially dependent and varies with the system parameters.

Effect of Molybdenum Coatings on the Accelerating Cavity Quality Factor

In this work, a detailed parametric study assessing the impact of low-conductivity coatings on the radio-frequency accelerating cavity quality factor and resonance frequency shift is presented. In particular, this study is aimed at proving the feasibility of molybdenum oxides deposited on copper to reduce the dark current in high-gradient applications due to its intrinsically high work function. In order to compute the effective surface impedance of the resulting layered structure, a transmission line-based approach is adopted. The present analysis demonstrates the potential effectiveness of molybdenum thin-films, which only slightly affects the accelerating cavity quality factor, with very low sensitivity to thickness and resistivity inhomogeneities.

Circularly Polarized Luminescence from Chiral Photonic Crystals of Caesium Lead Halide Perovskites

AbstractThe generation and detection of circularly polarized light (CPL) are of importance in many modern technologies such as digital communications, machine vision, bio‐imaging, and 3D displays. In this study, inspired by the fact that various species of plants and animals can efficiently produce and/or perceive CPL with chiral photonic crystal structures, efforts are made to fabricate luminescent chiral photonic crystals with caesium lead halide perovskites, a class of solution‐processable semiconductors that have excellent luminescence properties and readily tunable electronic band gaps. Coupling between the emission frequency of the perovskite and the cavity resonance frequency of the photonic crystal structure can be established at any desired point in the visible region, giving rise to CPL output with a dissymmetry factor up to −0.34. These results suggest a new approach to chiral light‐emitting materials and may contribute to the development of semiconductors with ordered microstructures.

An analytical method for phase noise evaluation in a microwave VCO stabilized by an interferometry structure

This study proposes a set of mathematical formulations to model a microwave interferometric structure to stabilize a free-running oscillator. The microwave interferometric structure employed a carrier suppression system to lock the voltage-controlled oscillator (VCO) frequency to a high-Q resonator and clean up the phase noise spectrum. Analytical relations were derived by modeling the system's stabilization loop components with an equivalent system transfer function. This model optimized the feedback loop circuits for a reliable frequency-locked structure with suitable spectral purity using well-known linear system methods. Thus, the phase noise of an oscillator's output signal locked to a high-Q cavity resonant frequency could be predicted and optimized. Furthermore, a prototype cavity-stabilized oscillator (CSO) system with commercial components wasimplemented to validate the proposed model. The results demonstrated that approximately 40 dB phase noise reduction at 10 kHz offset frequency was obtained at X-band, exhibiting good agreement with the proposed mathematical model. Moreover, the prototype structure's feedback circuits were designed, and their performance was validated using simulation and measurement data.

Power Dependent Resonant Frequency of a Microwave Cavity Due to Magnetic Levitation

The fact that a magnet levitates above a superconductor is a fascinating consequence of the interaction between electromagnetic fields and the macroscopic quantum state of the superconductor. Such field-matter interactions, which include the Meissner and Josephson effects, combined with superconducting devices, such as low-loss superconducting microwave cavities, are emerging as key elements used in quantum computers. One technique that can be used to monitor the levitation of a magnet is to place the magnet within a superconducting microwave cavity and monitor the microwave resonance of that cavity. Here, we report measurements of the change in resonance frequency of the microwave cavity with the Meissner-levitated permanent magnet. The cavity resonance changes because the magnet perturbs the radio-frequency field inside the microwave cavity. The changes in resonant frequency and quality factor were measured as functions of input power and temperature. The observed power-dependent variations are explained in terms of the power dependence of the London penetration depth.

Frequency-Dependent Squeezed Vacuum Source for the Advanced Virgo Gravitational-Wave Detector.

In this Letter, we present the design and performance of the frequency-dependent squeezed vacuum source that will be used for the broadband quantum noise reduction of the Advanced Virgo Plus gravitational-wave detector in the upcoming observation run. The frequency-dependent squeezed field is generated by a phase rotation of a frequency-independent squeezed state through a 285m long, high-finesse, near-detuned optical resonator. With about 8.5dB of generated squeezing, up to 5.6dB of quantum noise suppression has been measured at high frequency while close to the filter cavity resonance frequency, the intracavity losses limit this value to about 2dB. Frequency-dependent squeezing is produced with a rotation frequency stability of about 6Hz rms, which is maintained over the long term. The achieved results fulfill the frequency dependent squeezed vacuum source requirements for Advanced Virgo Plus. With the current squeezing source, considering also the estimated squeezing degradation induced by the interferometer, we expect a reduction of the quantum shot noise and radiation pressure noise of up to 4.5dB and 2dB, respectively.

Dynamics of cavitating tip vortex

The three-dimensional dynamic behaviour of a tip vortex generated by a NACA $66_2$ -415 hydrofoil is investigated under wetted flow and cavitating conditions using time-resolved tomographic particle image velocimetry. Two main cavitation modes are studied, namely the breathing and double-helical modes. The time-averaged flow field consists of a system of two streamwise vortices for all three conditions. The shape of the tip vortex resembles that of the cavitation mode, instead of a circular cylinder. Multi-scale vortical structures are captured in the instantaneous flow field. The surface oscillation of the cavity contributes to the growth of Kelvin–Helmholtz instability over the tip vortex, leading to the onset of hairpin vortices. Stronger spanwise interaction between the tip vortex and flow separation of the hydrofoil is produced by cavitation, further intensifying the perturbation growth. The proper orthogonal decomposition analysis gives insight into the relationship between cavity oscillation and vortex instability. Two major types of unstable modes of the tip vortex are obtained, leading to serpentine centreline displacement and elliptical deformation motion. The selection of the dominant unstable mode is associated with cavity surface oscillation. For the wetted flow condition, the displacement mode dominates the growth of vortex perturbation, while for breathing mode cavitation, the most energetic unstable mode changes into an elliptical deformation pattern, the disturbance energy of which is negligible in the wetted flow condition. Consistency is found between the peak frequency of the deformation mode and the cavity resonance frequency, indicating the contribution of cavity oscillation to the disturbance growth and breakdown of the tip vortex.

On-chip topological THz biosensors

On-chip terahertz (THz) biosensors have enormous potential in advancing the development of integrable devices for real-time, label-free, and noninvasive detection of proteins, DNA, and cancerous tissue. However, high absorption of THz waves by water necessitates evanescent field-based biosensing. The conventional on-chip THz biosensors with small mode confinement volumes and scaling sensitivity to defects severely limit the interaction of analyte with the electromagnetic field. Here, we reveal a topological waveguide cavity system with topologically protected propagating interfacial modes, exhibiting evanescent waves with an out-of-plane field extent of 0.3λ0, where λ0 is the wavelength corresponding to the cavity resonance frequency. Our experiments involving biomolecule detection and leaf-hydration monitoring show that the near-field of high-Q topological cavity resonances accurately detects minute frequency shifts over extended periods, facilitating real-time sensing and monitoring of biological matter. Implementation of topologically protected evanescent fields in waveguide-cavity systems will enhance on-chip THz biosensing.

Parameter Optimization for Modulation-Enhanced External Cavity Resonant Frequency in Fiber Fault Detection

Fiber fault detection is crucial for maintaining the quality of optical communication, especially in well-established optical access networks with extended distances and a growing number of subscribers. However, the increasing insertion loss in fiber links presents challenges for traditional fault-detection methods in capturing fault echoes. To overcome these limitations, we propose a modulation-enhanced external-cavity-resonant-frequency method that utilizes a laser for fault echo reception, providing improved sensitivity compared to traditional photodetector-based methods. Our previous work focused on analyzing key parameters, such as sensitivity and spatial resolution, but did not consider practical aspects of selecting optimal modulation parameters. In this study, we develop a model based on Lang–Kobayashi rate equations for current-modulated optical feedback lasers and validate it through experimental investigations. Our findings reveal that optimal detection performance is achieved with a modulation depth of 0.048, a frequency sweeping range of 0.6 times the laser relaxation oscillation frequency, and a frequency sweeping step of 0.1 times the external cavity resonant frequency.

Feedforward resonance control for the European X-ray free electron laser high duty cycle upgrade

The High Duty Cycle (HDC) upgrade is a proposed improvement to the existing European X-ray Free Electron Laser (EuXFEL) to extend the pulsed RF duty factor from the actual value of around 1% to more than 5% up to Continuous Wave (CW). To implement this upgrade, the loaded quality factor (QL) of the superconducting cavities will increase by more than one order of magnitude. This will result in shrinking the cavity bandwidth to values as low as a few Hertz. Since the Lorentz Force Detuning (LFD) experienced during the accelerating field buildup is of hundreds of Hertz, the Low-Level RF (LLRF) system has to accurately track and control the cavity resonance frequency to obtain the desired accelerating gradient. Moreover, ponderomotive instabilities have to be suppressed to achieve stability during beam acceleration. Since LFD is a repetitive disturbance in cavity frequency, the correction to its effects can be implemented as a feedforward compensation on the piezoelectric tuners of the cavity. Initial results on the simulation of feedforward resonance control in the HDC regime are discussed in this proceeding.

Cavity Quantum Electrodynamics with Hyperbolic van der Waals Materials.

The ground-state properties and excitation energies of a quantum emitter can be modified in the ultrastrong coupling regime of cavity quantum electrodynamics (QED) where the light-matter interaction strength becomes comparable to the cavity resonance frequency. Recent studies have started to explore the possibility of controlling an electronic material by embedding it in a cavity that confines electromagnetic fields in deep subwavelength scales. Currently, there is a strong interest in realizing ultrastrong-coupling cavity QED in the terahertz (THz) part of the spectrum, since most of the elementary excitations of quantum materials are in this frequency range. We propose and discuss a promising platform to achieve this goal based on a two-dimensional electronic material encapsulated by a planar cavity consisting of ultrathin polar van der Waals crystals. As a concrete setup, we show that nanometer-thick hexagonal boron nitride layers should allow one to reach the ultrastrong coupling regime for single-electron cyclotron resonance in a bilayer graphene. The proposed cavity platform can be realized by a wide variety of thin dielectric materials with hyperbolic dispersions. Consequently, van der Waals heterostructures hold the promise of becoming a versatile playground for exploring the ultrastrong-coupling physics of cavity QED materials.

A Case Study Comparing Active Vs. Passive Enablers for Vehicle Interior Noise Reduction

The implementation of enablers on a luxury sport utility vehicle is used to illustrate the development process for reduction of road noise. The vehicle in this case study was launched into production with two tuned mass dampers for reduction of low frequency road noise content which was amplified by frame modes. Additionally, resonators were integrated into the wheels (rims) to address the dominant cavity resonance frequencies. The results of this successful production implementation are illustrated herein. An RNC (road noise cancellation) system was integrated into the case vehicle to assess its performance relative to the passive enablers listed above. This production representative (embedded software solution) RNC system utilized the vehicle's existing audio system for creation of active noise to cancel noise content which was predicted using accelerometers mounted to the vehicle chassis. A comparison of in-vehicle noise indicated a significant reduction at low frequencies (at all seating locations) when utilizing the active noise control solution. These noise improvements are coupled with a vehicle mass reduction of greater than 4 kg, when compared to the passive enabler solution.