Extraction of lateral eigenmode properties in thin film bulk acoustic wave resonator from interferometric measurements

Kimmo Kokkonen, Tuomas Pensala, Johanna Meltaus, Matti Kaivola

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

A heterodyne laser interferometer is used to study acoustic wave fields excited in a 1.8 GHz AlN thin film bulk acoustic wave resonator. The electrical response of the resonator exhibits a strong thickness resonance onto which spurious modes, caused by lateral standing plate waves, are superposed. Optical interferometer measurements are used to extract dispersion curves of the laterally propagating waves responsible for the spurious responses. A discrete eigenmode spectrum due to the finite lateral dimensions of the resonator is observed. An equivalent circuit model for a multimode resonator is fitted to the mechanical resonator response extracted along a single curve in the dispersion diagram, and is used to determine properties, such as Q-values, of the individual lateral eigenmodes. Measured wave field images, extracted dispersion curves, and the eigenmode spectrum with the model fitting results are presented.
Original languageEnglish
Article number173502
Pages (from-to)1-3
Number of pages3
JournalApplied Physics Letters
Volume96
Issue number17
DOIs
Publication statusPublished - 2010
MoE publication typeA1 Journal article-refereed

Keywords

  • BAW
  • interferometry
  • spurious modes

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