Propagation Characteristics Of Surface Waves Research Articles

Study of surface acoustic waves on the {110} plane of gallium arsenide

Piezoelectric semiconductors such as GaAs are of interest for signal processing devices due to the possibility of monolithic integration of surface-acoustic-wave (SAW) -based devices and active electronic circuits on the same substrate. The common crystal orientation of GaAs for these applications has been the {100} cut. In this paper the characteristics of surface wave propagation in the {110} plane of GaAs, which supports both the Rayleigh and the Bleustein–Gulyaev surface wave modes, are investigated. Several test devices have been fabricated and studied using laser probe and S-parameter measurement techniques. The SAW velocity, attenuation, piezoelectric coupling constant, slowness surface, beam profile, and the transducer characteristics have been measured, and the experimental results agree well with the theoretical calculations for both types of the surface wave modes.

Characteristics of surface wave propagation along the edge of an anisotropic laminated semi-infinite plate

Characteristics of surface wave propagation along the edge of semi-infinite plates (edge waves) are investigated by means of the semi-exact method proposed by the present authors. First, the characteristics of edge waves for semi-infinite isotropic plates are calculated and the results are compared with those obtained by other published approximate theories and by the FEM. The semi-exact method is found to completely describe symmetric and antisymmetric modes of edge wave propagation. An approximate relation between the velocity of energy propagation and Poisson's ratio is obtained for the first antisymmetric mode in the high frequency range. Next, the frequency spectra are discussed for a semi-infinite unidirectionally reinforced carbon/epoxy laminated plate and for a hybrid composite laminated plate which consists of carbon/epoxy and glass/epoxy layers.

Characteristics of seismic waves composing Hawaiian volcanic tremor and gas‐piston events observed by a near‐source array

A correlation method, specifically designed for describing the characteristics of a complex wave field, is applied to volcanic tremor and gas‐piston events recorded by a semicircular array of GEOS instruments set at the foot of the Puu Oo crater on the east rift of Kilauea volcano, Hawaii. The spatial patterns of correlation coefficients obtained as functions of frequency for the three components of motion over the entire array are similar for gas‐piston events and tremor, and clearly depict dispersive waves propagating across the array from the direction of Puu Oo. The wave fields are composed of comparable amounts of Rayleigh and Love waves propagating with similar and extremely slow phase velocities ranging from 700 m/s at 2 Hz to 300 m/s at 8 Hz. The highly cracked solidified lava flow on which the array was deployed, and subjacent structure of alternating lava and ash layers formed during repeated eruptions of Puu Oo since 1983, appear to be responsible for the low velocities observed. The results from Puu Oo stand in sharp contrast to those obtained in an experiment conducted in 1976 on the partially solidified lava lake of Kilauea Iki. Rayleigh waves were not observed in Kilauea Iki, but well‐developed trains of Love waves were seen to propagate there with velocities twice as high as those observed near Puu Oo. These differences in the propagation characteristics of surface waves at the two sites may be attributed to the presence of a soft horizontal layer of molten rock in Kilauea Iki, which may have lowered the phase velocity of Rayleigh waves more drastically than that of Love waves, resulting in severe scattering of the Rayleigh wave mode. On the other hand, the thin superficial pahoehoe flow under our array at Puu Oo may have favored the development of vertical columnar joints more extensively at this location than at Kilauea Iki, which may have reduced the shear moduli controlling the Love wave mode. The average phase velocities in the frequency band from 2 to 5 Hz found at Puu Oo are roughly similar to those determined for tremor at Klyuchevskoy volcano, Kamchatka, but the frequency dependence appears much stronger at Puu Oo.

Magnetostatic wave propagation in YIG double layers

Calculations are presented for the magnetostatic surface wave propagation characteristics in single-crystal yttrium-iron-garnet (YIG) double layers with arbitrary direction of magnetization. The induced uniaxial magnetic anisotropy field is assumed to be different in the two layers; hence, the magnetization in one layer is aligned at an angle with respect to the magnetization direction in the other layer. The magnetostatic field interactions between layers depend on the angle between the two magnetization directions and on the separation between the two YIG layers. The wave propagation directions and time delays in each layer can be strongly affected by the use of an applied magnetic field and the magnetostatic coupling between the two layers, as well as by the uniaxial anisotropy energy in each layer.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Characteristics of surface wave propagation along the edge of an anisotropic laminated semi-infinite plate.

Characteristics of surface wave propagation along the edge of semi-infinise plates (edge wave) are investigated by means of the semi-exact method proposed by the present authors. First, numerical results for the edge wave of isotropic semi-infinite plates are calculated and compared with those obtained by other published approximate theories and the FEM. The semi-exact method is found to be able to give the complete characteristics of symmetric and antisymmetric modes of the edge wave. An approximate relation between the velocity of energy propagation and Poisson's ratio is obtained for the first antisymmetric mode in high frequency. Next, frequency spectra are clarified for a unidirectional carbon/epoxy laminated semi-infinite plate and a hybrid composite laminated plate which consists of carbon/epoxy and glass/epoxy layers.

Study of Slow Surface Waves in 70-GHz Solid-Plasma Waveguide Utilizing Maximum-Entropy Method

The 70-GHz slow surface wave propagation characteristics in a transversely-magnetized partially-filled parallel-plate solid-plasma waveguide were studied by an interferometric method using n-type InSb at 77 K. Spectral analysis using the maximum-entropy method was applied to the interferometric patterns thus obtained. The results clearly indicate the existence of three different propagation modes, and their propgation constants were determined. One of these corresponds to the previously predicted slow surface wave mode, here confirmed experimentally for the first time. Surface wave resonance also takes place on this mode, and the maximum value of the phase constant, 5.5×103 m-1, was obtained. A relation between the estimated power density and the attenuation constant of these modes is suggested.

Comparison of magnetostatic surface wave propagation characteristics at 77 and 299 K

The propagation of magnetostatic surface waves in yttrium iron garnet at 77 K is reported. The bandwidth was increased by about 60%, the dispersion was reduced, and the required bias field for a given frequency of operation was decreased by over 20% as compared to room-temperature results. These results can be explained by the increase in the magnetization of yttrium iron garnet at 77 K. In addition, the minimum delay line insertion loss was reduced by 1–2 dB at the lower temperature.

Propagation of surface waves in inhomogeneous plasmas

Phase and attenuation measurements of a test wave enable us to verify the propagation characteristics of surface waves in inhomogeneous plasma columns.

Analysts of anisotropic single‐mode fibers

AbstractThe surface wave propagation characteristics of several isotropic single‐mode fibers are analyzed by applying the mode‐coupling theorem to left‐handed and right‐handed circularly polarized waves. In the gyrotropic fiber or unidirectional fiber, both polarized waves become eigenmodes and Faraday rotation occurs at linearly polarized wave incidence due to the difference in propagation constants. The rotation angle in the fiber in which the core and clad have the same anisotropy is identical to the rotation angle of a plane wave propagating in infinite gyrotropic media. The 45° Faraday rotator may be constructed by these fibers with sufficiently practical length.

Surface-wave propagation in an ocean basin with an anisotropic upper mantle: numerical modelling

Summary. The characteristics of surface-wave propagation in ocean basins are examined numerically for models with two types of anisotropic alignment in the upper mantle: one resulting from glide-plane slip in olivine with horizontal or vertical slip-planes, and the other from syntectonic recrystallization of olivine in a zone of horizontal shear. Glide-plane slip can cause highly anomalous inclined-Rayleigh particle-motion in the third-generalized mode (corresponding to the isotropic second-Rayleigh mode). The amplitude of this anomaly is rather insensitive to details of the structure. Syntectonic recrystallization can cause an anomalous combination of inclined-and tilted-Rayleigh motion in all modes. The variation with period of the amplitude of the anomaly in the fundamental mode can indicate the approximate depth to the anisotropic layer. In both types of alignment, the sense of tilt and the inclination varies with direction of propagation in a manner characteristic of the structural symmetry.

Investigation of Leaky-Wave Propagation in Rotated Y Cuts of LiNbO3

LiNbO, is examined as to its suitability for ex- tended time delays using the wraparound concept. In this connection the propagation characteristics of surface waves on rotated (about the X axis) I' cuts are investigated for propaga- tion directions such that the sagittal plane is in the neighbor- hood of the YZ plane. These crystal cuts and directions of propagation are of considerable interest inasmuch as they contain planes of propagation which exhibit large electrome- chanical coupling and favorable anisotropy (extended beam collimation). These same orientations also contain directions of propagations in which leaky wave modes can appear. Leaky-wave propagation is possible for directions of propaga- tion which do not lie in the YZ plane for a range of rotated Y cuts, wherein the outward surface normal makes an angle of between -5 and -85 (or equivalently - 175 to -95) with respect to the positive Y axis of the crystal measured toward the positive Z axis. Electric probe measurement of piezo- electric surface waves have been made on rotated Y cuts which support leaky-wave propagation. Velocity profiles on three rotated Y-cut planes were obtained for each of the surface- wave, shear-wave, and leaky-wave solutions. general, the surface-wave mode is evanescent in the transverse direction so long as its velocity is less than the lowest bulk shear-wave velocity in the substrate material.5 Since the sur- face wave propagation velocity on a cylindrical surface in- creases as the ratio of the radius to wavelength approaches unity,' the lowest shear wave will be the lowest velocity mode at some point and the evanescent condition is no longer satis- fied. Mode conversion is then a distinct possibility, unless the particle displacements of the two modes are orthogonal to each other, thus preventing mode coupling. On the other hand, there exists an upper limit on the radius of curvature if mode conversion, leading to significant attenua- tion, developes along all or part of the propagation path in the curved region. In that case, and for purely practical reasons, the curved path length must be minimized by reducing the curvature radius as much as is possible, subject only to the lower limit criteria discussed previously. The large functional bandwidth and favorable anisotropy inherent in YZ LiNbOj renders it an attractive candidate for wide band information storage. It is shown in this paper that the angle between the helical propagation path (sagittal plane) and the YZ plane in LiNhO, must be small if significant losses on the curved portions of the path are to be avoided. These additional losses arise from the coupling between the surface wave and the lowest bulk shear wave in one quadrant of rotated Y cuts, where the velocity of the latter is lower than that of the surface wave and the particle motions of the two waves have a common component and are therefore coupled. EXPERIMENTAL DATA

Propagation Characteristics of Surface Elastic Waves on Ba (Ti0.95Zr0.05)O3 Ceramic Plates

Propagation characteristics of surface waves on Ba(Ti0.95Zr0.05)O3 ceramics have been studied under various conditions. The Ba(Ti0.95Zr0.05)O3 ceramic has two second-phase transition temperatures, around 0 and 54 °C, and has a Curie temperature of 96 °C. The attenuation constant for surface wave propagation has a peak value in the vicinity of the phase transition temperature. The logarithmic decrement is nearly independent of frequency over the range 0.8–1.8 MHz. Also, the attenuation is nearly constant for the range of input voltage below 40 V, but increases rapidly beyond 40 V. It is concluded that for the input voltage with small amplitude, the attenuation due to the dielectric loss is predominant, but the attenuation due to the hysteresis mechanism increases for an input voltage above 40 V. Furthermore, it is found that at the second-phase transition temperature, the conversion efficiency of the transducer attains the peak value, while the propagation velocity takes a minimum value.

Thermal Diffusion of Injected Impurities into Ceramic Dielectrics

First, sintered ceramics of BaTiO3, CaTiO3, Pb(Ti, Zr)O3, and TiO2 were prepared by the conventional method. Then, the disks were coated with powders of metal oxide or carbonate such as CuO, Bi2O3, La2O3, PbO, Co2O3, Cr2O3, Fe2O3, MnCO3 and SrCO3. The injection of various impurities by thermal diffusion were made by heating the ceramice at 1100°-1450°C for 0.5-4h. For these specimens, diffusion depth of the injected impurities into the base ceramics, distribution patterns of the impurities in the ceramics, and effects of the impurities on the electrical properties of the ceramic dielectrics were examined systematically. Main results obtained are summarized as follows.1) Ceramic dielectrics with injected impurities by means of thermal diffusion show properties differing from those with impurities added during the powder stage of the conventional ceramic technique.2) The distribution patterns of the injected impurities were examined by X-ray microanalyzer for CaTiO3 semiconducting ceramic with the injected bismuth oxide, TiO2, ceramic with the injected copper oxide, and BaTiO3 ceramic with the injected manganese oxide. As a result, it was ascertained that the injected impurities were located at the grain boundaries.3) By modifying the characteristics of the grain boundaries by means of thermal diffusion of the injected impurities, we can control the electrical and piezoelectric properties of ceramic dielectrics such as the electromechanical coupling coefficient of BaTiO3 ceramic or the propagation characteristics of surface wave on the PZT ceramic.

NONMAGNETOSTATIC VOLUME AND SURFACE WAVE MODES ON GYROMAGNETIC YIG ROD WAVEGUIDES

Electromagnetic surface waves on a gyromagnetic single crystalline YIG rod waveguide were measured by a disturbing body technique in a surface wave resonator. Both the volume and surface-mode surface waves were measured under conditions when magnetostatic analysis is not valid. Experimental results are presented to show that important nonmagnetostatic characteristics of surface wave propagation revealed in the dispersion plot have all been verified.

A Study On Propagation Characteristics Of Surface Wave On Sedimentary Layers Based On Earthquake Observations

Seismological observation on Osaka Plain has revealed the existence of ATOYURE» > . » > . * > . • > , or surface wave in the sedimentary layer with a period of 1.0 to 1.5 seconds, which follows the principal motion. ATOYURE is characteristic of earthquake motion observed on the sedimentary layer of the plain. The results of our study, based on the analysis of observed waveforms and the determination of theoretical dispersion curves, show that or surface wave in the sedimentary layer, indicates the characteristics of both Love and Rayleigh waves in the wide frequency range from 0. 3 to 1. 5Hz. Evidently surface wave, with a characteristic dispersion, propagates from the boundary region between the plain and surrounding mountains throughout the plain. INTRODUCTION Ever since the great Mexican earthquake of 1985, surface wave (motion with a relatively long period) propagation through the sedimentary layer of a plain has been regarded as a key factor in discussing earthquake motion in a plain. Prior to the earthquake in Mexico, surface wave propagation through the sedimentary layer of a plain had been observed in the Osaka Plain and reported as ATOYURE. Importance had not been attached to this motion which, though limited in scale, had not caused significant damage. However, this motion is an important factor in ensuring the safety of a large and long-span structure in the event of earthquake: the acceleration amplitude of ATOYURE sometimes exceeds that of principal motion, though ATOYURE, occurring after the principal motion, is a simple motion without a harmonic. This report based on earthquake observation records and the results of theoretical analysis, to discusses the characteristics of surface wave propagation through the sedimentary layer of the Osaka Plain. Transactions on the Built Environment vol 3, © 1993 WIT Press, www.witpress.com, ISSN 1743-3509