The relation between creeping waves, leaky waves, and surface waves

In this paper, we examine the creeping wave propagation wavenumbers, modal impedance, and field behavior on a dielectric coated circular cylinder. The physical interpretation is assisted by comparing the cylinder's pole waves with the leaky waves and surface waves that occur on a flat, grounded dielectric slab. The propagation wavenumbers and modal impedance are computed in the complex wavenumber plane. The cylinder propagation wavenumbers come from a transcendental equation involving Hankel functions, which are entire functions of complex order, whereas for the slab, branch-point singularities are present. This difference is examined, so that one can better understand how a coated cylinder behaves like a flat slab, when the cylinder radius is large. It is found that for the cylinder, the Stokes line for the asymptotic expansion of the Hankel function plays a role that is similar to the planar slab branch cut.     

Ultrahigh-frequency surface electromagnetic waves in an open waveguide

An experiment in which guided propagation of surface electromagnetic waves (SEWs) on a free curved metal-dielectric interface was observed in the ultrahigh-frequency band (at frequencies of 850 and 1200 MHz) is described. The data on signal propagation over various paths and under various propagation conditions is presented. It has been found that the decrease of the wave field with increasing distance from the source follows the exponential law.     

Acoustic surface waves on paratellurite

Numerical calculations of surface-wave properties and their temperature dependence have been carried out for the principal planes of paratellurite. The surface-wave velocity is shown to have large anisotropy, and several directions with zero temperature coefficients of delay are found.     

激光激发源对声表面波的影响

利用激光激发声表面波及光差分技术研究激光源对声表面波的影响。实验中利用了Nd∶YAG脉冲激光器激发超声,采用632nm的He-Ne激光器基于光束偏转法的光差分检测系统,测量了铝样品表面的声表面波,获得了很好的信号。在此基础上研究了激发源的形状和能量对激发的声表面波幅度的影响。同时从热弹和融蚀机制下讨论激光声表面波的产生。在这两种机制下,声表面波的幅度发生了很大的变化。随着激光能量密度的增加,声表面波的幅度由线性变化转换为非线性变化。这一结果对激光激发声表面波理论研究有一定的指导意义。     

Acoustic surface waves on isopaustic glass

The construction of transducers for launching surface waves on nonpiezoelectric substrates is described. It is shown that efficient launching can be obtained using zinc-oxide films with a thickness of less than 5% the acoustic wavelength. Amorphous substrates can be used, and results are given for isopaustic glass which enables temperature stability of a few parts per million per degree Celsius to be obtained.     

Diffraction of surface magnetostatic waves by surface cavities on ferromagnetic film

The diffraction problem of the scattering of surface magnetostatic waves by shallow rectangular and circular cavities on the surface of a ferromagnetic film that is tangentially magnetized with respect to the surface is numerically analyzed in the magnetostatic approximation.     

Frequency response of an interdigital transducer for excitation of surface elastic waves

Excitation of elastic waves in a piezoelectric solid by an interdigital transducer, in terms of a simplified model, has been analyzed using Lamb's integral solution. The transducer generates three types of disturbances propagating at the velocities of irrotational, equivoluminal, and Rayleigh waves. While the amplitudes of the former two waves diminish as the three-half power of the distance from the transducer, that of the latter does not decay with distance on the surface. Dependence of particle displacement of the waves on electric fields, number of electrodes, electrode width, and wave numbers has been derived. It has been shown that a conventional interdigital transducer, in which all the electrode widths and all the spacings are respectively equal among themselves, can respond to fundamental and odd harmonic excitations, but not to the even harmonics. Means to improve the insertion loss and the bandwidth of the transducer are discussed. A flat overall frequency response can be synthesized by parallel operation of two or more transducers, the fundamental frequencies of which are properly staggered.     

A quasi-field equivalent circuit of an interdigital transducer of surface acoustic waves

A new equivalent circuit of a surface-acoustic-wave (SAW) interdigital transducer (IDT) is proposed. A method using this circuit for calculation of the device’s gain-frequency characteristic and impedance is described. The fingers of the transducer can be arbitrarily shaped and positioned. The electrode current is obtained via the rigorous calculation of the SAW-related charge in the piezoelectric substrate and of the charge induced by the former charge in the transducer electrodes. The method allows design of SAW devices with an arbitrary complex finger structure and a multilayer substrate.     

Horizontal shear surface waves on corrugated surfaces

Experiments have been performed on horizontal shear surface-wave propagation along a corrugated surface. The results are in agreement with approximate theories used in analogous electromagnetic problems.     

Visualisation of surface acoustic waves

A simple method for acoustic-surface-wave visualisation is described which is applicable to both piezoelectric and non-piezoelectric surfaces. Briefly, a uniform layer of small particles, comparable to the wavelength, is distributed over the acoustic surface. The acoustic-beam pattern of an incident surface wave is then traced out by scattering the particles out of the propagation path. Experiments at 100 MHz on lithium-niobate surfaces are described.     

Parametric amplification of acoustic surface waves on CdS

We report some experimental results on the parametric interaction of codirected s.a.w. in photoconducting CdS. This interaction takes place through the 2nd-order electric field associated with the bunching of carriers. Below threshold conditions, we directly observed both parametric attenuation and amplification with a 30 dB dynamic range. At the highest electric level of the pump available on our apparatus, 16 dBm, the parametric gain is about 10 dB. Beyond the threshold conditions, we observed only a parametric attenuation.     

Diffraction spreading of surface waves on LiNbO3

The far-field diffraction spreading of surface acoustic waves on y cut LiNbO3, has been measured in two directions. For propagation along z, the beam is much narrower than for the isotropic case, and along a direction at 21.9° to z it is broader; both observations are in semiquantitative agreement with an analysis based on a parabolic approximation for the velocity surface in the neighbourhood of these directions.     

The effects of surface acoustic waves on the optical properties ofAlGaAs-GaAs quantum-well structures

The effects of a propagating surface acoustic wave (SAW) on the transitions in single- and multiple-quantum-well structures and the change in their absorption and refractive index are presented here. The fundamental difference between the effects of an applied electric field and a propagating SAW are those due to a linear and a nonlinear induced field, respectively. The electron and hole energy eigenvalues and envelope functions of the unperturbed structure are determined. The effect of the SAW-induced strain and electric fields on the confining potential of the quantum-well (QW) structure is then calculated and the energy eigenvalues and envelope functions for this perturbed case are determined. The complex refractive index of the structure is then determined for both the perturbed and unperturbed cases, to give the change in refractive index and the absorption coefficient as a function of SAW wavelength, amplitude, barrier composition, well width, and number of wells. The wavelength (λ_ac) and power of the SAW were found to be important in setting the induced changes in the refractive index     

Multiple surface plasmon polariton waves

Multiple surface plasmon polariton (SPP) waves were experimentally observed for the first time at the planar interface of a metal thin film and a chiral sculptured thin film assembled in the Kretschmann configuration. All launched SPP waves had the same frequency but different phase speeds.     

Horizontal shear surface waves on a laminated composite

The existence is demonstrated of a new type of acoustic surface wave that has a horizontally polarised shear displacement and which propagates along the free surface of a halfspace comprised of a periodically layered composite. This wave contrary to other types of dispersive waves, has unique bandpass and bandstop dispersive characteristics that suggest new filter applications.     

Shear surface elastic waves on large amplitude gratings

Calculations have been made of the dispersion curves for spolarised surface elastic waves propagating across large amplitude gratings of sinusoidal and sawtooth profiles, by use of a method based on the Rayleigh hypothesis.     

Comments on representation of surface leaky waves on uniplanartransmission lines

This paper compares partial waves approximating a surface leaky wave on a uniplanar transmission line with substrate surface waves supported by its substrate. It is shown that their field distributions and the propagation constants differ. These differences increase with rising leakage constant, and with the growing distance of the corresponding pole of the Green function from the real axis on the spectral variable complex plane. The reported findings are demonstrated on the slotline     

Nonlinear behaviour of magnetostatic surface waves

The higher-power behaviour of magnetostatic surface waves propagating at right angles to a magnetic bias field in a y.i.g. single-crystal slab has been investigated experimentally. The conditions for coincidence of the surface modes and the high-power subsidiary absorption are discussed.