Interaction Of Surface Acoustic Waves Research Articles

Nonreciprocity of surface acoustic waves coupled to spin waves in a ferromagnetic bilayer with noncollinear layer magnetizations

Nonreciprocity of propagation of surface acoustic waves (SAWs) in the microwave frequency band can be achieved using the magnetoelastic interaction of SAWs with spin waves (SWs) propagating in magnetic heterostructures. Recent works have shown that the ultimate isolation of a counterpropagating hybridized SAW/SW is achieved in heterostructures consisting of a synthetic antiferromagnet—a ferromagnetic (FM) bilayer with antiferromagnetic Ruderman-Kittel-Kasuya-Yosida interlayer coupling—placed on top of a piezoelectric acoustic waveguide. In this work, we study in detail a more practical and technologically simpler system based on an FM bilayer, where layers are coupled by only dipole-dipole interaction, and having noncollinear magnetizations of the FM layers. A weak in-plane anisotropy with noncollinear easy axes in the layers is shown to be the only essential factor for the realization of strongly nonreciprocal propagation of a hybridized SAW/SW. We formulate requirements for the relative orientation of the layer’s magnetizations and wave propagation direction necessary to realize an efficient SAW isolator, and demonstrate examples of SAW transmission characteristics which prove the possibility of achieving an isolation exceeding 50 dB for a submillimeter-long FM bilayer with insertion losses of just a few decibels more than those of a pure SAW device. In addition to relative fabrication simplicity, the proposed magnetoelastic heterostructure exhibits a reasonable robustness in respect to deviations in the anisotropy axes and/or bias field directions—an important benefit for device mass production. Published by the American Physical Society 2024

О возможности создания эффективных устройств на поверхностных акустических волнах на частотах выше 6 ГГц

In the paper the interaction of surface acoustic waves (SAWs) with reflectors and interdigital transducers (IDTs) with high aspect ratio electrodes (HAR-electrodes) are investigated. The conditions for the SAW resonant reflection and propagation and the effective IDT conversion of the SAW power into electrical power at the load have been obtained. The real possibility of the effective SAW devices creation (filters, delay lines, resonators, RFID tags) at frequencies above 6 GHz (up to 12-15 GHz) using HAR-electrodes was demonstrated.

Coherent surface acoustic wave–spin wave interactions detected by micro-focused Brillouin light scattering spectroscopy

We investigated the interaction of surface acoustic waves and spin waves with spatial resolution by micro-focused Brillouin light scattering spectroscopy in a Co40Fe40B20(10 nm) ferromagnetic layer on a LiNbO3-piezoelectric substrate. We experimentally demonstrate that the magnetoelastic excitation of magnons by phonons is coherent by studying the interference of light scattered off generated magnons and annihilated phonons. We find a pronounced spatial dependence of the phonon annihilation and magnon excitation, which we map as a function of the magnetic field. The coupling efficiency of the surface acoustic waves (SAWs) and the spin waves is characterized by a magnetic field-dependent decay of the SAWs amplitude.

Surface Acoustic Wave Interaction with a Mixture of Oxygen and Nitrogen

Parameters of surface acoustic waves (SAW) are very sensible to change of physical conditions of a propagation medium. In the classical theory formulation, the waves are guided along the boundary of semi-infinity solid state and free space. A real situation is more complex and a medium commonly consists of two physical components: a solid substrate and a gaseous or liquid environment. In the case of stress-free substrate, the strongest impact on SAW properties have surface electrical and mechanical conditions determined by solids or liquids adhering to the boundary. This impact is utilised for constructing sensors for different gases and vapours e.g. (Jakubik et al., 2007; Hejczyk et al., 2011; Jasek et al., 2012). The influence of gaseous environment on the SAW properties is usually very weak and ignored. However, in certain condition it can be significant enough to be applied to sensor construction. In general, it concerns Rayleigh wave devices where energy leakage phenomenon is perceptible, especially when the gas being detected considerably changes the density of environment. The paper presents the results of experiments with oxygen-nitrogen mixture. Their primary aim was focused on finding the dependence of resonant frequency and attenuation in SAW resonator on parameters and concentrations of the gas in the environment.

Acoustic resonance effects and cavitation in SAW aerosol generation

The interaction of surface acoustic waves (SAWs) with liquids enables the production of aerosols with adjustable droplet sizes in the micrometer range expelled from a very compact source. Understanding the nonlinear acousto-hydrodynamics of SAWs with a regulated micro-scale liquid film is essential for acousto-microfluidics platforms, particularly aerosol generators. In this study, we demonstrate the presence of micro-cavitation in a MHz-frequency SAW aerosol generation platform, which is touted as a leap in aerosol technology with versatile application fields including biomolecule inhalation therapy, micro-chromatography and spectroscopy, olfactory displays, and material deposition. Using analysis methods with high temporal and spatial resolution, we demonstrate that SAWs stabilize spatially arranged liquid micro-domes atop the generator's surface. Our experiments show that these liquid domes become acoustic resonators with highly fluctuating pressure amplitudes that can even nucleate cavitation bubbles, as supported by analytical modeling. The observed fragmentation of liquid domes indicates the participation of three droplet generation mechanisms, including cavitation and capillary-wave instabilities. During aerosol generation, the cavitation bubbles contribute to the ejection of droplets from the liquid domes and also explain observed microstructural damage patterns on the chip surface eventually caused by cavitation-based erosion.

Simulations of surface acoustic wave interactions on a sessile droplet using a three-dimensional multiphase lattice Boltzmann model.

This study reports the development of a three-dimensional numerical model for acoustic interactions with a microscale sessile droplet under surface acoustic wave (SAW) excitation using the lattice Boltzmann method (LBM). We first validate the model before SAW interactions are added. The results demonstrate good agreement with the analytical results for thermodynamic consistency, Laplace law, static contact angle on a flat surface, and droplet oscillation. We then investigate SAW interactions on the droplet, with resonant frequencies ranging 61.7-250.1 MHz. According to our findings, an increase in wave amplitude elicits an increase in streaming velocity inside the droplet, causing internal mixing, and further increase in wave amplitude leads to pumping and jetting. The boundaries of wave amplitude at various resonant frequencies are predicted for mixing, pumping, and jetting modes. The modeling predictions on the roles of forces (SAW, interfacial tension, inertia, and viscosity) on the dynamics of mixing, pumping, and jetting of a droplet are in good agreement with observations and experimental data. The model is further applied to investigate the effects of SAW substrate surface wettability, viscosity ratio, and interfacial tension on SAW actuation onto the droplet. This work demonstrates the capability of the LBM in the investigation of acoustic wave interactions between SAW and a liquid medium.

Acoustoelectronic interaction in metal island films

The interaction of surface acoustic waves with conduction electrons of island films of various metals was investigated. Island films were formed on the surface of piezoelectric crystalline substrates: Lithium Niobate, Bismuth Germanate, and Piezoquartz. It is experimentally obtained that the surface acoustic wave attenuation as a function of film resistance has a characteristic maximum, and that the velocity changes from the velocity at the free surface of the substrate to that at the metallized surface.

Nonreciprocal Magnetoacoustic Waves in Dipolar-Coupled Ferromagnetic Bilayers

We study the interaction of surface acoustic waves (SAWs) with spin waves (SWs) in a ${\mathrm{Co}}_{40}{\mathrm{Fe}}_{40}{\mathrm{B}}_{20}$/$\mathrm{Au}$/${\mathrm{Ni}}_{81}{\mathrm{Fe}}_{19}$ system composed of two ferromagnetic layers separated by a nonmagnetic $\mathrm{Au}$ spacer layer. Because of interlayer magnetic dipolar coupling between the two ferromagnetic layers, a symmetric and an antisymmetric SW mode form, which both show a highly nondegenerate dispersion relation for oppositely propagating SWs. Due to magnetoacoustic SAW-SW interaction, we observe highly nonreciprocal SAW transmission in the piezoelectric-ferromagnetic hybrid device. We experimentally and theoretically characterize the magnetoacoustic wave propagation as a function of frequency, wave vector, and external magnetic field magnitude and orientation. Additionally, we demonstrate that the nonreciprocal SW dispersion of a coupled magnetic bilayer is highly tuneable and not limited to ultrathin magnetic films, in contrast to the nonreciprocity induced by the interfacial Dzyaloshinskii-Moriya interaction. Therefore, magnetoacoustic coupling in ferromagnetic multilayers provides a promising route towards building efficient acoustic isolators.

Atomic-molecular and acoustoelectronic processes in a rarefied gas medium

The features of the interaction of surface acoustic waves with a rarefied gas medium are considered. The relationship between acoustoelectronic and atomic-molecular phenomena accompany the processes of adsorption and desorption of atoms and molecules on the surface of a solid is analyzed. Two types of sorption processes are discussed: adsorption and desorption of gas on a solid surface; adsorption and vapour desorption. In the first process, the temperature of the adsorbent is higher than the boiling point of the corresponding liquid. In the second, the adsorbent temperature corresponds to the area of coexistence vapour and liquid. In each case, the use of vacuum technology in the processes under investigation is noted.

Nonreciprocal Dzyaloshinskii-Moriya Magnetoacoustic Waves.

We study the interaction of surface acoustic waves with spin waves in ultrathin CoFeB/Pt bilayers. Because of the interfacial Dzyaloshinskii-Moriya interaction (DMI), the spin wave dispersion is nondegenerate for oppositely propagating spin waves in CoFeB/Pt. In combination with the additional nonreciprocity of the magnetoacoustic coupling itself, which is independent of the DMI, highly nonreciprocal acoustic wave transmission through the magnetic film is observed. We systematically characterize the magnetoacoustic wave propagation in a thickness series of CoFeB(d)/Pt samples as a function of magnetic field magnitude and direction, and at frequencies up to 7GHz. We quantitatively model our results to extract the strength of the DMI and magnetoacoustic driving fields.

Molecular dynamics modeling of nonlinear propagation of surface acoustic waves

A new computational setup suitable for the exploration of nonlinear effects in free propagation and dissipation of surface acoustic waves (SAWs) is developed based on the molecular dynamics (MD) simulation method. First applications of the computational model demonstrate the ability of atomistic simulations to reproduce the key features of the nonlinear SAW evolution, which are distinct from their well-known counterparts in bulk wave propagation. In particular, the MD simulations predict the increasing localization of the acoustic energy near the surface of the substrate during the nonlinear sharpening of the wave profile, which leads to the formation of a shock front with characteristic cusps in the horizontal strain and velocity profiles. The peak values of surface strain and velocity associated with the cusps can significantly exceed those of the initial wave. Some of the effects revealed in the MD simulations are outside the capabilities of continuum-level models and have not been explored so far. These include the observation of an unusual quadratic correction to the dispersion relation at short wavelengths defined by the frequency-dependent localization of SAWs near the surface of the substrate, the establishment of a new mechanism of the energy dissipation at the SAW shock front, where SAW harmonics generated at the limit of frequency up-conversion transform very effectively into clouds of phonon wave packets descending into the substrate bulk, and the generation of localized zones of plastic deformation at a substantial distance from the wave source. Overall, the MD methodology developed for atomistic modeling of free SAW propagation not only enables detailed analysis of the intrinsic properties of nonlinear SAWs and verification of theoretical models but also opens up a broad range of opportunities for investigation of acoustically induced surface processes, material modification by SAWs, and the interaction of SAWs with preexisting crystal defects and other material heterogeneities.

Surface Acoustic Waves-Localized Plasmon Interaction in Pillared Phononic Crystals

We study numerically the interaction of surface acoustic waves propagating at the surface of a multilayer structure (the so-called Sezawa waves) with localized surface plasmons at the bottom of metallic pillars deposited on the substrate. The pillars are made of gold and the multilayer structure is constituted by a layer of gold on a silicon substrate and covered by a thin spacer of dielectric material. We are interested in localized plasmons, which are the analog of metal-dielectric-metal surface plasmons. The physical characteristics of these plasmons, such as their eigenvalues and absorption or reflection spectra, are modulated by surface acoustic waves due to deformation of the structure in the vicinity of the pillars. The surface waves are generated in the area in front of the pillars deposited on the substrate. Two types of acoustic modes are envisioned to interact with the localized plasmons, namely, confined modes associated with the local resonances of the pillars and the propagating Sezawa modes that deform the structure in the vicinity of the surface. We discuss the efficiency of phonon-plasmon coupling for both types of modes and select those that can be useful for an experimental realization based on this platform. Also, we show that, besides the plasmon frequency, the phonon-plasmon coupling magnitude strength is sensitive to the distance between the pillars, which reveals the role of interactions between the pillars on the coupling. The geometrical parameters are chosen such that the acoustic waves are in the sub-GHz range and the plasmons are around the telecommunication wavelength of 1.55 mu m. This work may help with the design of optomechanical devices that can be controlled by fast coherent acoustics and facilitate applications involving enhanced sound-light interactions, such as light modulation.

Removal of spoiling materials from solar panel surfaces by applying surface acoustic waves

Surface acoustic wave (SAW) technologies have been widely utilized for sensitive surface cleaning and particle steering applications in micro-electro-mechanical system (MEMS). This study investigates application of SAWs for cleaning of solar PV panel surfaces. Spoiling of photovoltaic (PV) solar panel surfaces is one of major problems that can reduce energy efficiency of PV solar energy systems in outdoor conditions. Rough mechanical cleaning methods can easily damage surface of panels and hence they can reduce efficient working life-span of panels. Therefore, sensitive and electronically controllable self-cleaning techniques are needed to keep PV panel surface cleaner. This study presents a theoretical analysis for detachment phenomenon of dust particles in interaction with SAWs. These analysis considers adhesion forces and effects of gravity in cleaning process and results reveal underlying mechanisms involving in particle detachment process. We derive sufficient conditions that are required for removal of a dust particle from inclined panel surfaces in case of SAW interactions. Experimental studies are conducted with spoiled PV solar panels, and cleaning effects of SAWs on solar panel surface are demonstrated.

Optimal configuration of the waveguide acousto-optic TE-TM polarization mode convertor on X-cut lithium niobate substrate

An excitation, distribution, and interaction of surface acoustic waves (SAW) with the guided light in integrated optical structures on X-cut lithium niobate substrates were studied. The resonance excitation frequencies, the spatial SAW distribution and the TE-TM optical mode conversion efficiency were investigated. An optimal configuration and most suited material of interdigital transducer (IDT) for integrated acousto-optic devices were found.

Влияние конфигурации и материала встречно-штыревых преобразователей на возбуждение поверхностных и псевдоповерхностных акустических волн в подложках ниобата лития

The excitation, distribution, and interaction of surface acoustic waves (SAW) and pseudo surface acoustic waves (PSAW) in a X-cut lithium niobate substrates were investigated. The resonant excitation frequencies, the wave distribution velocities and the dispersion characteristics were determined for each of the wave types. The influence of the interdigital transducer (IDT) material on the excitation efficiency and the interaction between investigated wave types was found out. The interdigital transducer material and configuration requirements for integrated acousto-optic devices were determined.

Interaction of acoustic surface waves induced by inter-digital transducer with wall thinning defect in pipe structure

Most structural health monitoring (SHM) systems require transducers permanently attached to or integrated with the monitored structure to form a type of smart structure. It is difficult to permanently attach traditional ultrasonic transducers for non-destructive testing of structures for health monitoring. However, inter-digital transducers (IDTs) can be considered for on-site SHM because of the small size and economic efficiency of the IDT sensor. In this paper, an alternative sensor approach is proposed using IDT rather than conventional transducers to identify the interaction of surface acoustic waves (SAWs) with a wall-thinning defect. The SAWs generated by IDT sensors are modeled using the finite element analysis method. Acoustic wave propagation behavior in plate and pipe structures was reviewed, and the effect of the curvature of curved plate was investigated. From the interaction behavior observed between SAWs and a wallthinning defect in the pipe, which was determined using numerical simulation and tests, a novel concept is proposed for characterizing wall-thinning defects in pipelines.

Combining Mass Spectrometry, Surface Acoustic Wave Interaction Analysis, and Cell Viability Assays for Characterization of Shiga Toxin Subtypes of Pathogenic Escherichia coli Bacteria.

Shiga toxin (Stx)-producing Escherichia coli (STEC) and enterohemorrhagic E.coli (EHEC) as a human pathogenic subgroup of STEC are characterized by releasing Stx AB5-toxin as the major virulence factor. Worldwide disseminated EHEC strains cause sporadic infections and outbreaks in the human population and swine pathogenic STEC strains represent greatly feared pathogens in pig breeding and fattening plants. Among the various Stx subtypes, Stx1a and Stx2a are of eminent clinical importance in human infections being associated with life-threatening hemorrhagic colitis and hemolytic uremic syndrome, whereas Stx2e subtype is associated with porcine edema disease with a generalized fatal outcome for the animals. Binding toward the glycosphingolipid globotriaosylceramide (Gb3Cer) is a common feature of all Stx subtypes analyzed so far. Here, we report on the development of a matched strategy combining (i) miniaturized one-step affinity purification of native Stx subtypes from culture supernatant of bacterial wild-type strains using Gb3-functionalized magnetic beads, (ii) structural analysis and identification of Stx holotoxins by electrospray ionization ion mobility mass spectrometry (ESI MS), (iii) functional Stx-receptor real-time interaction analysis employing the surface acoustic wave (SAW) technology, and (iv) Vero cell culture assays for determining Stx-caused cytotoxic effects. Structural investigations revealed diagnostic tryptic peptide ions for purified Stx1a, Stx2a, and Stx2e, respectively, and functional analysis resulted in characteristic binding kinetics of each Stx subtype. Cytotoxicity studies revealed differing toxin-mediated cell damage ranked with Stx1a > Stx2a > Stx2e. Collectively, this matched procedure represents a promising clinical application for the characterization of life-endangering Stx subtypes at the protein level.

Interaction between lithotripsy-induced surface acoustic waves and pre-existing cracks

The interaction between pre-existing cracks and surface acoustic waves (SAW) in lithotripsy is investigated. Surface acoustic waves are generated at a water-glass interface by an incident shock wave produced by the spark discharge of a nano pulse lithotripsy (NPL) device or an electromagnetic shock wave lithotripsy (SWL) source. Evidence of SAW, including leaky Rayleigh wave and Scholte wave, will be presented based on photoelastic imaging and numerical stimulations using COMSOL. A clear correlation between SAW and the location of the maximum tensile stress produced on the glass boundary has been identified, which can lead to ring-like fractures on a flat glass surface exposed to NPL-generated spherically divergent shock waves. To simulate cavitation-induced surface pitting in SWL, pre-existing crack will be introduced on the glass surface by microindentation using a Vickers or Knoop indenter. The interaction of SAW with the pre-existing cracks will be examined to characterize crack extension and branching as a function of their location and orientation to the incident shock wave.

Acoustic-Electric Properties of Graphene under the Influence of a Surface Acoustic Waves and an External DC Field

ABSTRACTMeasurements of the induced acoustoelectric (IAEC) current in graphene subjected to a surface acoustic wave (SAW) discovered a quantisized character of acoustoelectric current at low bias voltage (Vbias) . The quantisized nature of IAEC has been obtained in all measurements as a result of interaction of SAW and an applied an external electric field. The acoustoelectric currents were studied near the point of electrical neutrality at room temperature. Raman spectra of graphene under the in-situ SAW influence and at an external electric field bias are presented.

Resonant attenuation of surface acoustic waves by a disordered monolayer of microspheres

Attenuation of surface acoustic waves (SAWs) by a disordered monolayer of polystyrene microspheres is investigated. Surface acoustic wave packets are generated by a pair of crossed laser pulses in a glass substrate coated with a thin aluminum film and detected via the diffraction of a probe laser beam. When a 170 μm-wide strip of micron-sized spheres is placed on the substrate between the excitation and detection spots, strong resonant attenuation of SAWs near 240 MHz is observed. The attenuation is caused by the interaction of SAWs with a contact resonance of the microspheres, as confirmed by acoustic dispersion measurements on the microsphere-coated area. Frequency-selective attenuation of SAWs by such a locally resonant metamaterial may lead to reconfigurable SAW devices and sensors, which can be easily manufactured via self-assembly techniques.