Surface Acoustic Resonator Research Articles

On-chip stimulated Brillouin scattering via surface acoustic waves

Surface acoustic wave devices are ubiquitously used for signal processing and filtering, as well as mechanical, chemical, and biological sensing and show promise as quantum transducers. While surface acoustic waves (SAWs) are primarily excited and driven using electromechanical coupling and interdigital transducers, there is a strong desire for novel methods that enable the coherent excitation and detection of SAWs all-optically interfacing with photonic integrated circuits. In this work, we numerically model and experimentally demonstrate SAW excitation in integrated photonic waveguides made from GeAsSe glass via backward stimulated Brillouin scattering (SBS). We measure a Brillouin gain coefficient of 203 W−1 m−1 for the surface acoustic resonance at 3.81 GHz, with a linewidth narrowed to 20 MHz. Experimental access to this new regime of SBS not only opens up opportunities for novel on-chip sensing applications by harnessing the waveguide surface but also paves the way for strong Brillouin interactions in materials lacking sufficient acoustic guidance in the waveguide core, as well as the excitation of SAWs in non-piezoelectric materials.

Controlling photons by phonons via giant atom in a waveguide QED setup.

We investigate the single photon scattering in a phonon-photon hybrid system in the waveguide quantum electrodynamics (QED) scheme. In our consideration, an artificial giant atom, which is dressed by the phonons in a surface acoustic wave resonator, interacts with a coupled resonator waveguide (CRW) nonlocally via two connecting sites. Together with the interference effect by the nonlocal coupling, the phonon serves as a controller to the transport of the photon in the waveguide. On the one hand, the coupling strength between the giant atom and the surface acoustic wave resonator modulates the width of the transmission valley or window in the near resonant regime. On the other hand, the two reflective peaks induced by the Rabi splitting degrade into a single one when the giant atom is large detuned from the surface acoustic resonator, which implies an effective dispersive coupling. Our study paves the way for the potential application of giant atoms in the hybrid system.

Nuclear surface acoustic resonance with spin-rotation coupling

We show that, under an appropriate out-of-plane static magnetic field, nuclear spins in a thin specimen on a surface acoustic wave (SAW) cavity can be resonantly excited and detected through spin-rotation coupling. Since such a SAW cavity can have the quality factor as high as $10^{4}$ and the mode volume as small as $10^{-2}$ mm$^{3}$ the signal-to-noise ratio in detecting the resonance is estimated to be quite high. We argue that detecting nuclear spin resonance of a single flake of an atomically-thin layer of two-dimensional semiconductor, which has so far been beyond hope with the conventional inductive method, can be a realistic target with the proposed scheme.

Supported Model Membranes for Biosensing Applications - Optical Oxytocin Binding Assay

Solid-supported phospholipid bilayers are versatile model structures for mimicking the biological cell membrane, and are increasingly utilized as functional interface components of biosensors and other bio-micro- and nanofluidic devices. In the context of biosensor development, membrane-embedded peptides have gained importance as bio-recognition elements, targeting diverse analytes including proteins, nucleic acids, bacteria, metal ions, enzymes and antibodies. For example, the neuropeptide oxytocin has a key role during labor and lactation as well as in the development of social behavior. Divalent cations such as Zn2+ and Cu2+ vitally affect the activity of oxytocin upon binding. Deviations in the quantity and whereby binding of such ions to oxytocin are associated with diseases; e.g., multiple sclerosis, Alzheimer, and autism spectrum disorder (ASD). We developed an immunofluorescence assay to verify and quantify lipid bilayer membrane-integration of oxytocin-cholesterol conjugate, which was designed and synthesized as membrane-associated recognition element for a surface acoustic resonance (SAR) sensor. In our study, a microfluidic open-volume superfusion device, the Biopen, was used to deposit small unilamellar vesicles, prepared from 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) and oxytocin-conjugated cholesterol, onto a glass surface, where they transformed into extended patches of planar surface-supported bilayer. Thereafter, oxytocin endogenous carrier protein neurophysin-1 (primary antibody) and a fluorescently tagged secondary antibody, were sequentially delivered to the membrane. An antibody binding dependence on oxytocin-concentration was determined by means of fluorescence microscopy, and an optimal concentration for sensor applications was established. The fluorescence assay can be directly transferred to the SAR sensor, where a supported bilayer is established as sensing layer in order to quantify interactions between oxytocin and molecules of interest in a quantitative manner with high sensitivity, fundamentally supporting the development of new diagnostic and therapeutic options for the early detection of neurological and neurodegenerative conditions.

A high-performance lab-on-a-chip liquid sensor employing surface acoustic wave resonance: part II

We recently introduced an in-liquid sensing concept based on surface acoustic resonance (SAR) in a lab-on-a-chip resonant device with one electrical port. The 185 MHz one-port SAR sensor has a sensitivity comparable to other surface acoustic wave (SAW) in-liquid sensors, while offering a high quality factor (Q) in water, low impedance, and fairly low susceptibility to viscous damping. In this work, we present significant design and performance enhancements of the original sensor presented in part I. A novel ‘lateral energy confinement’ (LEC) design is introduced, where the spatially varying reflectivity of the SAW reflectors enables strong SAW localization inside the sensing domain at resonance. An improvement in mass-sensitivity greater than 100% at resonance is achieved, while the measurement noise stays below 0.5 ppm. Sensing performance was evaluated through real-time measurements of the binding of 40 nm neutravidin-coated SiO2 nanoparticles to a biotin-labeled lipid bilayer. Two complementary sensing parameters are studied, the shift of resonance frequency and the shift of conductance magnitude at resonance.

Designing a Non-invasive Surface Acoustic Resonator for Ultra-high Sensitive Ethanol Detection for an On-the-spot Health Monitoring System

Surface acoustic wave (SAW) sensors–based on piezoelectric crystal resonators–are extremely sensitive to even very small perturbations in the external atmosphere, because the energy associated with the acoustic waves is confined to the crystal surface. In this study, we present a critical review of the recent researches and developments predominantly used for SAW-based organic vapor sensors, especially ethanol. Besides highlighting their potential to realize real-time ethanol sensing, their drawbacks such as indirect sensing, invasive, time initializing, and low reliability, are properly discussed. The study investigates a proposed YZ-lithium niobate piezoelectric substrate with interdigital transducers patterned on the surface. Design of the resonator plays an important role in improving mass sensitivity, particularly the sensing area. Accordingly, a tin dioxide (SnO2) layer with a specific thickness is generated on the surface of the sensor because of its high affinity to ethanol molecules. To determine the values of sensor configuration without facing the practical problems and the long theoretical calculation time, it is shown that the mass sensitivity of SAW sensors can be calculated by a simple three-dimensional (3-D) finite element analysis (FEA) using a commercial finite-element platform. In design validation step, different concentrations of ethanol are applied to investigate the acoustic wave properties of the sensor. The FEA data are used to obtain the surface and bulk total displacements of the sensor and fast Fourier transform (FFT) on output spectrum. The sensor could develop into highly sensitive and fast responsive structure so that a positive intensity shift of 0.18e-2 RIU is observed when the sensor is exposed to 15 ppm ethanol. It is capable of continuously monitoring the ethanol gas whether as an ultra-high sensitive sensor or switching applications for medical and industrial purposes.

Finite-element analysis of scattering parameters of surface acoustic wave bandpass filter formed on barium titanate thin film

ABSTRACTThe frequency dependence of scattering parameters of interdigital surface acoustic wave transducers placed on ferroelectric barium titanate (BaTiO3) epitaxial film in c-phase coated over magnesium oxide has been studied using the finite-element method (FEM) approach along with the perfectly matched layer (PML) technique. The interdigital transducer which has a comb-like structure with aluminum electrodes excites the mechanical wave. The distance between the fingers allows tuning the frequency properties of the wave propagation. The magnesium oxide is taken as the substrate. The two-dimensional model of two-port surface acoustic wave filter is created to calculate scattering parameters and to show how to design the fixture in COMSOLTM. Some practical computational challenges of finite element modeling of SAW devices in COMSOLTM are shown. The effect of lattice misfit strain on acoustic properties of heterostructures of BaTiO3 epitaxial film in c-phase at room temperature is discussed in present article for two low-frequency surface acoustic resonances.

Three-Dimensional Analysis of Surface Acoustic Resonator for Ultra-High Sensitive Ethanol Disclosure as Non-Invasive Biosensor

Due to the increasing demand on ethanol gas sensors for several applications such as automation transportation or environmental monitoring the need for more sensitive and reliable sensors with an on spot response time is required Indirect sensing invasive bulky time initializing and low reliability in strip tests are some drawbacks of ethanol sensing measurements at the present To overcome these leakages there is focused on modelling and simulation of a proposed ethanol sensor based on surface acoustic wave technique using finite element method

A surface acoustic resonator with template-patterned interdigitated fingers

Printed electronics techniques show promise as high-throughput, low-cost methods for fabricating micro-scale device features. In this work, we demonstrate a SAW resonator fabricated through a printing process. Silver nanoparticle ink is introduced to a vapor-permeable template that is patterned with the desired SAW resonator metallization. After the solvent in the ink evaporates, the nanoparticles within the patterned template tightly pack to form the device metallization. Interdigitated resonator electrodes with widths and spacing ranging from 500nm to 1μm were patterned on lithium niobate, corresponding to center frequencies of 2.1–2.4GHz. The maximum quality factor was 13. Limitations and potential process improvements are discussed to improve resonator quality factor in future work.

Surface optomechanics: calculating optically excited acoustical whispering gallery modes in microspheres

Stimulated Brillouin scattering recently allowed experimental excitation of surface acoustic resonances in micro-devices, enabling vibration at rates in the range of 50 MHz to 12 GHz. The experimental availability of such mechanical whispering gallery modes in photonic-MEMS raises questions on their structure and spectral distribution. Here we calculate the form and frequency of such vibrational surface whispering gallery modes, revealing diverse types of surface vibrations including longitudinal, transverse, and Rayleigh-type deformations. We parametrically investigate these various modes by changing their orders in the azimuthal, radial, and polar directions to reveal different vibrational structures including mechanical resonances that are localized near the interface with the environment where they can sense changes in the surroundings.

The use of guided surface acoustic resonances in the determination of the thin film elastic tensor

A Brillouin light scattering investigation of thin supported films shows that the measurement of resonances within the continuum of excitations together with the dispersion of discrete surface acoustic modes such as the Rayleigh and Sezawa waves, yields valuable additional information. In the present study, an analysis of the combined data results in the precise determination of four independent components of the film elastic tensor of elastically anisotropic, polycrystalline tungsten carbide (W2C) films for which the single crystal elastic constants are not known.

Roughness induced surface acoustic resonances

The vibrational and electronic spectra of a semi-infinite crystal with a planar surface is modified in presence of surface inhomogeneities or roughness such as ridges or grooves, quantum wires or tips… Using a Green's function formalism, we present an exact numerical method for obtaining the variation of the density of states associated with the adsorption of a ridge on a flat surface or with a groove cut into an otherwise planar surface. This general method is applied to the determination of the acoustic resonances of shear horizontal polarization associated with such deterministic surface protuberances or indentations. The positions and widths of the peaks in the total or local densities of states give the frequencies and lifetimes of the resonances, which may be more or less pronounced features depending on the relative parameters of the substrate and ridge materials. We also investigate the modifications of these acoustic surface shape resonances due to the interaction between two such defects. This calculation can also be transposed to the study of electronic structure of a wire near a flat surface, in the framework of an effective mass model.