SAW Propagation Research Articles

Depolarization of the scattered light on internal reflection from surface acoustic waves on fused quartz. I. Theory

The theory of light scattering on internal reflection from surface acoustic waves (SAW’s) for the geometry where the incident plane is perpendicular to the SAW propagation direction is described. The surface corrugation and the acoustically induced optical polarized fields are calculated and the appropriate polarization driven wave equation is solved. The scattering of both s- and p-polarized incident light is discussed. In this theory, we predict that the intensity of light on internal reflection from SAW on fused quartz is very strong near the grazing angles for both s- and p-polarizations of the incident light and the scattering light is depolarized. Furthermore, we predict that the scattered light is left elliptically polarized if the incident light is s-polarized and right elliptically polarized if the incident light is p-polarized. A simple physical model is proposed to explain the depolarization effect.

Depolarization of the scattered light on internal reflection from surface acoustic waves on fused quartz. II. Experiment

The intensity of light scattered by surface acoustic waves (SAW’s) on internal reflection for fused quartz medium was measured for the geometry where the incident light is perpendicular to the SAW propagation direction. ZnO thin-film interdigital transducers are used for generating SAW on fused quartz substrates. Measurements of the scattered light intensity give excellent agreement with theory. Either s- or p-polarized incident light is scattered by the SAW into s- and p-polarization states. The scattered light is left (right) elliptically polarized if the incident light is s(p)-polarized.

SAW Propagation Characteristics on α-Quartz with Arbitrary Cut

New modified temperature coefficients of elastic stiffnesses for alpha-quartz were obtained for better agreement with experiments. Using these constants, SAW propagation characteristics on alpha-quartz were calculated, and the results are presented in a series of contour maps. From these maps, many new cuts of plate with zero temperature coefficient were found and theoretical and experimental studies were conducted on one of them which had a more stable temperature dependence than the ST-cut.

Application of (Pb, Nd)(Ti, Mn, In)O3 Piezoelectric Ceramics to High Frequency SAW Filters

High frequency (250∼650 MHz) SAW filters have been fabricated using (Pb, Nd)(Ti, Mn, In)O3 piezoelectric ceramics with a fine grain size less than 1 µm. These ceramics shows the lowest SAW propagation losses that have been reported for piezoelectric ceramics such as Pb(Ti, Zr)O3 ceramics. The fabricated filters shows a good bandpass response of about 20 dB insertion loss and 25 dB out-of-band rejection. This indicates that these ceramics have high potential for use as materials in high frequency SAW applications.

K3Li2Nb5O15 and Pb2KNb5O15 Tungsten-Bronze Films for SAW Devices

Characteristics of SAW properties of tungsten-bronze layered structures of (K3Li2Nb5O15)/(substrate) and (Pb2KNb5O15)/(substrate) combinations have been calculated. Hetero-epitaxial growth of these tungsten bronze films have been also described. KLN single-crystal films have been successfully grown with good epitaxy onto KBN and sapphire substrates by the sputtering technique. The SAW propagation on a KLN film has been observed in a layered structure of (KLN)/(sapphire).

Surface-acoustic-wave propagation in paramagnets

We have investigated propagation of surface-acoustic waves SAW in the paramagnetic phases of Ce${\mathrm{Al}}_{2}$ and SmSb. The temperature dependence of the SAW velocity is well accounted for with a magnetoelastic coupling of the strain components to the crystal-field-split magnetic ions. In Ce${\mathrm{Al}}_{2}$ we found large magnetic field effects on the Rayleigh wave velocity at 4.3 K which can be qualitatively explained by the same magnetoelastic coupling. Contributions to the SAW velocities from rotationally invariant magnetoelastic interactions could be determined. In Ce${\mathrm{Al}}_{2}$ we found evidence for the magnetoacoustic analog of the Cotton-Mouton-Voigt effect for the SAW. It manifests itself as an amplitude modulated interference effect which we can qualitatively account for. This is the first time Rayleigh waves have been used to investigate the various analogous magnetoelastic effects known from previous acoustic bulk wave experiments.

An Analysis of Energy Storage Effects on SAW Propagation in Periodic Arrays

An Analysis of Energy Storage Effects on SAW Propagation in Periodic Arrays

Magnetostrictive Fe-Si thin films for tunable SAW devices

RF sputtered films of Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> Si <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> , where <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x \approx .7</tex> , deposited on YZ-LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> , have been used for magnetically variable surface acoustic wave devices. A 1 micron thick film one cm long in the SAW propagation direction had a relative SAW velocity change of 0.02% at 63 MHz and 0.05% at 189 MHz for applied fields of less than 50 Oe after annealing at 200°C for 30 minutes. Magnetic properties (M-H loops and magnetostriction) of the films were measured and correlated with the SAW properties.

Variable SAW delay line using amorphous TbFe&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;film

This paper describes a large SAW velocity change obtained in a delay line consisting of an amorphous TbFe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> film on a LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> substrate. When an external bias field of about 4 kOe was applied parallel to the direction of SAW propagation, the percentage velocity change attained was -0.27 %. The value of this change is several times as large as that previously reported. The delay line may be used for trimming a small amount of delay time and tuning oscillation frequencies in an SAW oscillator.

Precise Measurement of SAW Propagation Velocity on LiNbO3

Precise Measurement of SAW Propagation Velocity on LiNbO₃

Nonreciprocity of saw velocity on a magnetized ferrite substrate

AbstractSurface acoustic waves (SAW) propagating on piezoelectric materials are now utilized in practical devices such as filters and signal processing. However, only a few papers were reported on SAW propagation on magnetic materials. In this paper, the propagation characteristics of magnetoelastic Rayleigh waves on the YIG substrate are treated experimentally for the bias configuration where dc magnetic bias field is tangential to the substrate surface and oblique to the direction of propagation. The saturation magnetization of the YIG ferrite used for the experiment is 250 and the Rayleigh waves were excited and received by using ZnO thin‐film transducers. In this configuration, the nonreciprocity of surface wave was observed. Its velocity to the forward direction was found to be different from that in the reverse direction. The maximum amount of nonreciprocity obtained experimentally in this paper was approximately 150 ppm. This value is too small for the application, but the unidirectional transducer, the isolator and the device similar to the circulator may be constructed by using the nonreciprocal characteristics of surface wave velocities.

SAW propagation characteristics on LiNbO_3 with arbitrary cut

SAW propagation characteristics on LiNbO_3 with arbitrary cut

Photoconductivity study of semiconductors using the surface acoustic wave convolver

Photoconductivity study of a semiconductor using the SAW convolver is presented. The semiconductor is placed either on or a small distance above the SAW delay line. A fast rise time pulse of light is applied to the semiconductor surface through the piezoelectric substrate, and the resulting change in the semiconductor conductance is observed by the relaxation of the SAW propagation loss. This technique has the important advantage that no ohmic contact to the semiconductor is needed.

Observation of SAW Propagation Patterns by Optical Methods

Observation of SAW Propagation Patterns by Optical Methods

Electronically variable surface-acoustic-wave velocity and tunable SAW resonators

From measurements of shifts in the resonant frequency of SAW resonators, it has been observed that the SAW propagation velocity under an interdigital transducer varies continuously as a function of external resistive or capacitive loads. For Al on YZ LiNbO3 at 34 MHz, the velocity under a transducer can be varied over a 1.4% range. Resonators, using a transducer to control the cavity transit time, have been fabricated which are continuously tunable up to 60 kHz. Capacitances are found to be superior as tuning elements, owing to the severe degradation of the resonance caused by resistances.

Strain effects in SAW devices

An analytical model is developed to determine the velocity of surface acoustic waves in strained media. It is shown that, in addition to the variations in path length, the SAW propagation may depend significantly on the velocity change with strain.

Study of SAW propagation characteristics by frequency-translated holography

Under the condition of continuous acoustic generation the patterns of forward, backward, and standing SAW’s propagating on a y-cut z-propagating LiNbO3 crystal were observed clearly by the frequency-translated holographic technique. The parameters of surface-wave propagation velocity, reflectivity, and transmissivity for an interdigital transducer could be obtained by this technique.