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Nonlinear Surface Acoustic Waves

[an error occurred while processing this directive] The nonlinear propagation of high-amplitude surface acoustic wave pulses in polycrystalline metals and synthetic fused silica was studied and exhibited qualitatively different types of nonlinear behavior. An acoustic pulse excited by a nanosecond laser pulse through a strongly absorbing layer was detected at two probe spots along the propagation path with a dual-probe-beam deflection setup. For polycrystalline metals (such as steel, aluminum, copper) the compression of the surface acoustic pulse and formation of a narrow peak in the registered normal surface velocity corresponding to a shock front in the in-plane velocity were detected. For fused silica, the temporal extension of the surface acoustic pulse and formation of two sharp peaks in the normal surface velocity related to two shock fronts in the in-plane velocity were registered. This different nonlinear behavior depends on the sign of the nonlinear acoustic constant, which is positive for polycrystalline aluminum and negative for synthetic fused silica. The formation of shock fronts with frequency up-conversion processes can be used to advance into gigahertz and even terahertz frequency ranges. The characterization of solids by their nonlinear acoustic and elastic constants promises to be complimentary and more specific than the characterization based on the linear properties.

We are extending these studies to the ultra short pulse regime using femtosecond laser excitation.

  • Serguei Jerebtsov
  • Alexandre Kolomenski
  • Vladimir Lioubimov
  • Hans A. Schuessler



SIBOR

SIBOR Laboratory
Dr. Hans A. Schuessler
Texas A&M Physics Dept.



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