Coupling Of Surface Acoustic Waves Research Articles

Axial modes of acoustically coupled surface acoustic wave Fabry–Perot resonators

The distribution of resonant frequencies in single cavity and acoustically coupled surface acoustic wave grating resonators is investigated. The axial mode distribution is calculated using the transverse resonance method. The components of the resonator are represented by equivalent circuits whose parameters can be adjusted to conform to experimental values. Results showing the effect of cavity design parameters on the distribution of the resonant frequencies in resonators of bilaterally symmetric construction are presented.

Surface acoustic wave properties of aluminum gallium arsenide

Surface acoustic wave (SAW) properties are measured for {100}-cut, 〈100〉-propagating aluminum gallium arsenide (AlxGa1−xAs) with x=0.2 and 0.4. The parameters used to characterize these properties are SAW velocity, SAW attenuation, and piezoelectric coupling coefficient. The measured velocities are found to be substantially higher than those on GaAs in agreement with the theoretical predictions of Adachi. The attenuation is close to the corresponding attenuation on GaAs which is approximately 1 dB/μs. The piezoelectric coupling coefficient is measured using two independent methods and is found to be significantly higher than that of GaAs. This means that the transduction of energy from electrical to acoustical is more efficient and hence acoustic charge transport devices on AlxGa1−xAs substrates will require considerably less rf drive power. An extensive literature search has revealed no previous work, theoretical or experimental, characterizing attenuation or piezoelectric coupling of SAW on AlxGa1−xAs. The velocity has been predicted by Adachi based on a model formulated by Keyes, and has been measured by Sapriel, but the measured velocities reported herein correspond to the predicted values much better than the values measured by Sapriel. The measurement technique described has not, to the authors’ knowledge, been previously used for measurement of the piezoelectric coupling coefficient, and represents a convenient method of obtaining the SAW parameters experimentally.

Oscillations in the acousto-electric proximity coupling to a 2D electron gas

We report the first results on proximity coupling of surface acoustic waves to a two dimensional electron gas. A GaAs-Al x Ga 1− x As heterojunction was placed in close proximity to the surface of a piezoelectric substrate on which a surface acoustic wave was propagated. Oscillations in the attenuation of the surface wave, corresponding to the Shubnikov-de Haas oscillations in σ xx , were observed as a function of applied magnetic field. Break down of the σ xx = 0 state is seen at moderate power levels for the SAW. This is interpreted as either large current effects or due to spatial modulation of the Landau levels.

Proximity coupling of surface acoustic waves to a superconducting Al<inf>x</inf>O<inf>1-x</inf>film

We present the first preliminary results on proximity coupling of surface acoustic waves (SAW) to a superconducting Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> film. The aluminum film was evaporated onto a glass substrate in a partial pressure of oxygen. The glass was then placed, with the film face down, between a pair of SAW transducers on a piezoelectric LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> substrate. Mechanical coupling between film and SAW was very weak and any attenuation of the SAW by electron-phonon interaction could be neglected. The SAW was attenuated by the coupling to the film of the piezoelectric field that the SAW produced. We found a large decrease in attenuation when superconductivity starts to appear in the film.

DETECTION OF BOUND VORTEX-ANTIVORTEX PAIRS IN A SUPERCONDUCTING THIN FILM BY SURFACE ACOUSTIC WAVES

The possibility of detecting the normal cores of vortices in a superconducting thin film, by acoustoelectric coupling of surface acoustic waves to the local sheet resistivity of the film, is discussed. The attenuation of 700 MHz SAW's by a superconducting NbN film has already been reported. We find that the observed attenuation is proportional to the density of these vortices.

High Velocity and High Coupling Surface Acoustic Waves Using ZnO Films on Ceramic Substrates with High Acoustic Velocity

The layered structure comprising a c-axis normally oriented ZnO piezoelectric film and Al2O3, AlN and SiC ceramic substrates which have high surface acoustic wave velocity and small surface roughness has given both high phase velocity and high coupling k2 for the 0th (Rayleigh) mode, 1st (Sezawa) mode, and leaky mode surface acoustic waves.

High coupling and high velocity surface acoustic waves using a c-axis oriented ZnO film on translucent Al2O3 ceramics

The layered structure comprising a c-axis normally oriented ZnO piezoelectric film and a translucent Al2O3 ceramic substrate which has a high surface-acoustic-wave velocity and a small surface roughness has given both a high phase velocity Vp and a high coupling k2 for the 0th (Rayleigh) mode, 1st (Sezawa) mode, and leaky mode surface acoustic waves. The measured maximum values of k2 are 3.6% for the 0th mode at h/λ=0.45 where Vp is 3.2 km/s, 5.7% for the 1st mode at h/λ=0.21 where Vp is 5.6 km/s, and 6.7% for the leaky mode at h/λ=0.16 where Vp is 6.2 km/s, where the interdigital transducers are located at the interface in measuring the above values, and also electrically floating plane metals are on top of the ZnO film for the last two values.

Very Fast Signal Processors As a Result of the Coupling of Surface Acoustic Wave and Digital Technologies

The recent progress of the digital and the surface acoustic wave (SAW) technologies have made them compatible; and it is now possible to design signal-processing modules which benefit from the flexibility of the digital techniques and the very high computation speed of the SAW techniques. Very fast signal processors can now be built which are able to process several tens of megasamples per second and whose volume and power consumption are limited. This paper shows the compatibility of these technologies and the advantages yielded by their joint use. Several examples are described which relate to one- and two-dimensional Fourier and correlation processors.

Very Fast Signal Processors as a Result of the Coupling of Surface Acoustic Wave and Digital Technologies

The recent progress of the digital and the surface acoustic wave (SAW) technologies have made them compatible; and it is now possible to design signal-processing modules which benefit from the flexibility of the digital techniques and the very high computation speed of the SAW techniques. Very fast signal processors can now be built which are able to process several tens of megasamples per second and whose volume and power consumption are limited. This paper shows the compatibility of these technologies and the advantages yielded by their joint use. Several examples are described which relate to one- and two-dimensional Fourier and correlation processors.

Coupling of surface acoustic waves propagating in two separated piezoelectric media

The coupling of surface acoustic waves propagating in two separated piezoelectric media is studied using the perturbation theory of Auld. The results of the analysis are applied to two configurations using Bi12GeO20 and CdS crystals. It is found that the loss due to coupling is about 7 dB at 50 MHz in the cases of (111)-cut, [110]-prop. Bi12GeO20 and Y-cut, 60°-X prop. CdS combination. On étudie le couplage des ondes acoustiques de surface se propageant sur deux milieux piezo-eléctriques par la théorie de perturbation de Auld. Les resultats d'analyse sont appliqué's aux deux configurations des cristanx Bi12GeO20 et CdS. On trouve que la perte par couplage est environ de 7 dB a 50 MHz dans le cas de combination de (111)-coupe, [110]-prop. Bi12GeO20 et Y-coupe, 60°-X prop. CdS.

Electromechanical coupling of surface acoustic waves in the vicinity of the phase transition in triglycine sulfate

The temperature dependences of an effective piezoelectric constant have been determined in the vicinity of the Curie temperature in the presence of externally applied electric fields from simultaneous measurements of the temperature variations of the electromechanical coupling constant of surface acoustic waves and of the dielectric constant. It is shown that the experimental results can be explained on the assumption that piezoelectricity in triglycine sulfate is of an ’’induced’’ and not an ’’intrinsic’’ nature.