ELASTIC SURFACE WAVES IN Α-Quartz: OBSERVATION OF LEAKY SURFACE WAVES

Engan, Helge E.; Ingebrigtsen, K.A.; Tonning, A.

doi:10.1063/1.1754825

Cited by 63 publications

(7 citation statements)

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“…Examples of surface acoustic wave device types with a dominant shear horizontal polarization include surface transverse waves 14 (STWs), leaky SAWs 15 , surface skimming bulk waves 16 (SSBWs) and Love waves 17,18 . The Love wave configuration has been reported as having one of the highest mass sensitivities 19 .…”

Section: Introductionmentioning

confidence: 99%

Layer guided shear horizontally polarized acoustic plate modes

McHale

Newton

Martin

2002

Journal of Applied Physics

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The theoretical basis describing Love waves propagating on a finite thickness substrate covered by a finite thickness solid layer having a lower shear acoustic speed is considered. A generalized dispersion equation is derived for shear horizontally polarized acoustic waves in this system. Two types of solutions to the dispersion equation, both satisfying stress free boundary conditions at the free surfaces, are shown to exist.The first type of solution has a displacement that decays with depth into the substrate whilst the second does not. Analytical approximations to the solutions for a thin solid guiding layer show that these solutions can be considered as generalizations of Love waves and resonant shear horizontally polarized acoustic plate modes (SH-APM), respectively. Numerical solutions to the dispersion equation are developed and the spectrum of modes for thick guiding layers is examined with particular reference to sensor applications. As expected, increasing the thickness of the guiding layer leads to multiple Love wave modes. However, each of these Love wave modes is found to possess a set of shear horizontally polarized acoustic plate modes. As the guiding layer thickness is increased the Love wave speed decreases until at approximately v l /4f , where v l is the shear acoustic speed of the layer and f is the frequency, a sharp transition occurs in the Love wave speed from a value close to the shear acoustic speed of the substrate, v s , to one close to the shear acoustic speed of the layer, v l . A similar pattern is observed for the layer guided SH-APM's with an increase in the guiding layer thickness resulting in a sharp transition in the speed of the SH-APM towards a value close to that of the next lower SH-APM. It is shown that the appearance of the second Love wave mode is a result of a continuation of the lowest SH-APM associated with the previous Love wave mode. A physical interpretation is developed for the Love waves on the finite substrate and for the layer guided SH-APM's and from this interpretation it is suggested that layer guided SH-APM sensors could provide significantly enhanced mass sensitivity.

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Section: Introductionmentioning

confidence: 99%

Layer guided shear horizontally polarized acoustic plate modes

McHale

Newton

Martin

2002

Journal of Applied Physics

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“…For off-symmetry directions, the elastodynamics equations of motion having both inhomogeneous and homogeneous wave solutions, the (three-component) leaky SAW radiates its energy towards the bulk of the anisotropic medium (see Appendix A), as the leaky Rayleigh waves do at specific liquid-solid interfaces [68]. The velocity of the leaky SAW and the magnitude of its attenuation along the direction of propagation strongly depend on the perturbation of the orientation from the symmetry direction [69], but for many cases the radiation of energy is small enough that the leaky SAWs are easily observable in experimental conditions [70,71]. As the orientation of the direction of propagation approaches high-symmetry directions, the contribution of the bulk homogeneous wave in the construction of the SAW may however vanish, together with the damping of the leaky SAW in the direction of propagation, and the (three-component) leaky SAW turns into a generalized RW.…”

Section: Harmonic Fieldsmentioning

confidence: 99%

“…This wave propagates damped in the direction of propagation. Nevertheless, as for many cases the radiation of energy is small enough, the leaky SAW can easily be observable in experimental conditions [70,71]. Its properties are quite similar to those of a leaky SAW propagating at the interface between an ideal fluid and an isotropic elastic medium [68,127].…”

Section: Appendix A4 Quasi-bulk Surface Wave (Qbsw)mentioning

confidence: 99%

Elastic surface waves in crystals. Part 1: Review of the physics

et al. 2011

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We present a review of wave propagation at the surface of anisotropic media (crystal symmetries). The physics for media of cubic and hexagonal symmetries has been extensively studied based on analytical and semi-analytical methods. However, some controversies regarding surfaces waves and the use of different notations for the same modes require a review of the research done and a clarification of the terminology. In a companion paper we obtain the full-wave solution for the wave propagation at the surface of media with arbitrary symmetry (including cubic and hexagonal symmetries) using two spectral numerical modeling algorithms.

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“…1 ' 2 Both the HVPSAW and the PSAW are pseudo surface waves in the sense that they are a form of coupled modes that can exist on anisotropic free surfaces and consist of a linear combination of phase matched decaying and radiating partial modes that together satisfy the mechanically free surface boundary conditions. The decaying partial modes, DPM, are the components that decay with depth, whereas the radiating partial modes, RPM, are the components that radiate power into the substrate, resulting in an attenuation of the field amplitudes as the wave propagates.…”

Section: Basic Conceptsmentioning

confidence: 99%

PSEUDO AND HIGH VELOCITY PSEUDO SAWs

Cunha

2000

Int. J. Hi. Spe. Ele. Syst.

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This article discusses the characteristics of pseudo surface waves (PS AWs) and high velocity pseudo surface waves (HVPSAWs). The fundamental properties of these waves, the matrix method formulation, the different solution types due to crystal symmetry, early experiments on HVPSAWs, and practical applications of pseudo surface acoustic waves serve as an introduction. The solutions to the pseudo modes are discussed by analyzing the boundary condition function for several orientations. The relation between the radiating partial modes and the sagittal plane bulk slowness reveals new characteristics of the different symmetry types of H VPS AW, and helps classify and understand the pseudo modes. The acoustoelectric Poynting vector is used along different crystal symmetry orientations to reveal and discuss the pseudo SAW characteristics: penetration depth, declination of the power vector, and an estimation of power flow angle. Experimental data and numerical solutions of HVPS AW and PS AW along selected planes and orientations are discussed. This article concludes with a brief analysis of layered structures on different symmetry type substrates and a discussion of the layered pseudo surface wave properties. 203 Int. J. Hi. Spe. Ele. Syst. 2000.10:1069-1109. Downloaded from www.worldscientific.com by UNIVERSITY OF ILLINOIS AT URBANA CHAMPAIGN on 03/11/15. For personal use only.204 Int. J. Hi. Spe. Ele. Syst. 2000.10:1069-1109. Downloaded from www.worldscientific.com by UNIVERSITY OF ILLINOIS AT URBANA CHAMPAIGN on 03/11/15. For personal use only. Early Experiments on HVPSA WLike the PSAW, the experimental evidence for the HVPSAW goes back over two decades. Some of the early experiments that detected the HVPSAW classified this wave as: "longitudinal bulk wave," "surface skimming bulk wave," "shallow bulk acoustic wave," or "quasi-bulk acoustic surface wave"; mostly due to the proximity of the phase velocity to the planar longitudinal bulk wave velocity in the direction of propagation. 5 ' 6 ' 7 ' 8 ' 910 The name "surface skimming bulk wave" has also been used for both PSAW and HVPSAW in early publications. 6 ' 11 Since a bulk acoustic wave, BAW, in a piezoelectric material does not satisfy the mechanically free boundary conditions, the mode experimentally identified could not be a BAW .The existence of an independent high-velocity pseudo SAW mode was identified by researchers from Brillouin scattering experiments on cubic materials. 12 Jhunjhunwala also discussed the pseudo SAWs, grouping them as first or second order pseudo SAWs, according to the number of radiating partial modes. 13 As mentioned in 1.2, the HVPSAW might have one or two radiating partial modes, depending on the symmetry of the orientation of propagation. Therefore a classification according to the number of radiating partial modes is not appropriate. Reference 12 estimates the HVPSAW to have high loss for the gallium arsenide, GaAs, orientations discussed in that paper. This is not the case for other materials and orientations as discussed in this pape...

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ELASTIC SURFACE WAVES IN Α-Quartz: OBSERVATION OF LEAKY SURFACE WAVES

Abstract: Results are given of measuring the phase velocity of elastic surface waves in the three principal planes of α-quartz. The observation of a leaky surface wave is reported.

Cited by 63 publications

References 3 publications

Layer guided shear horizontally polarized acoustic plate modes

Layer guided shear horizontally polarized acoustic plate modes

Elastic surface waves in crystals. Part 1: Review of the physics

PSEUDO AND HIGH VELOCITY PSEUDO SAWs

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