Mass sensitivity of acoustic wave devices from group and phase velocity measurements

Glen McHale, Fabrice Martin, Michael Newton

Research output: Contribution to journalArticlepeer-review

Abstract

The effect of dispersion on acoustic wave sensors is considered. The discussion is focused upon layer guided surface acoustic waves (Love waves), which obtain their high mass sensitivity for the first Love wave mode by optimizing the guiding layer thickness, d, such that dsimilar tolambda(l)/4; the wavelength in the layer is given by lambda(l)=f/v(l) where f is the operating frequency and v(l) is the shear acoustic speed of the guiding layer. We show that this optimization of guiding layer thickness corresponds to strong dispersion so that the phase and group velocities can be quite different. From the definition of the phase velocity mass sensitivity, we show that it can be determined from either the slope of the curve of phase velocity with normalized guiding layer thickness, z=d/lambda(l), or from the phase and group velocities measured for a given guiding layer thickness. Experimental data for a poly(methylmethacrylate) polymer guiding layer on 36degrees XY Lithium Tantalate is presented. Measurements of phase velocity and group velocity determined by a network analyzer were obtained for systematically increasing guiding layer thicknesses; a pulse transit experiment was also used to provide independent confirmation of the group velocity data. Two independent estimates of the mass sensitivity are obtained for z=d/lambda(l), or from the phase and group velocities measured for a given guiding layer thickness. Experimental data for a poly(methylmethacrylate) polymer guiding layer on 36degrees XY Lithium Tantalate is presented. Measurements of phase velocity and group velocity determined by a network analyzer were obtained for systematically increasing guiding layer thicknesses; a pulse transit experiment was also used to provide independent confirmation of the group velocity data. Two independent estimates of the mass sensitivity are obtained for z=d/lambda(l)
Original languageEnglish
Pages (from-to)3368-3373
Number of pages6
JournalJournal of applied physics
Volume92
Issue number6
DOIs
Publication statusPublished - 15 Sep 2002

Keywords

  • Love wave
  • shear wave
  • sensor

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