Phonon Imaging at Ultrasonic Frequencies: The Dynamic Response on Anisotropic Solids
Recently there have been a number of ultrasonics experiments performed that elicit detailed information on the elastodynamic response of anisotropic solids to transient point-like forces. In this lecture I will be describing methods for computing the dynamic Green’s functions of anisotropic solids, and showing how these response functions are able to account for the observations. In these experiments small-aperture transducers or acoustic lenses are used to achieve wide-angle radiation and detection sensitivity as well as high spatial resolution. Many salient aspects of thermal phonon imaging, such as phonon focusing, polarization selectivity and mode conversion at surfaces also feature in these ultrasonic experiments, but there are neverthless significant differences. Unlike thermal phonons, the ultrasonic waves are coherent, and because their characteristic wavelengths are several orders of magnitude larger than those of phonons, the far field condition is not as well satisfied, and diffraction effects feature prominently. Various modes of excitation and detection exist, both broadband and monochromatic, some of which tend to disguise these diffraction effects, while others reveal them clearly.
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- Aki, K. and P. Richards, 1980, Quantitative Seismology (Freeman, San Francisco).Google Scholar
- Castagnede, B. and Y. Berthelot, 1992, J. Acoustique 5, 417.Google Scholar
- Cottam, M.G. and A.A. Maradudin, 1984, Surface Linear Response Functions, in: Surface Excitations, ed. V.M. Agranovich and R. Loudin (Elsevier, Amsterdam).Google Scholar
- Hutchings, D.A., 1988, Ultrasonic Generation by Pulsed Lasers, in: Physical Acoustics, Vol XVIII, ed. W.P. Mason and R.N. Thurston (Academic, Boston).Google Scholar
- Kim, K.Y., A.G. Every and W. Sachse, 1993a, to be published.Google Scholar
- Kim, K.Y., A.G. Every and W. Sachse, 1993b, to be published.Google Scholar
- Kim, K.Y., A.G. Every and W. Sachse, 1993c, to be published.Google Scholar
- Novikov, V.V. and L. Chernozatonskii, 1988, Sov. Phys. Acoust. 34, 215.Google Scholar
- Sachse, W., A.G. Every and M.O. Thompson, 1990, Am. Soc. Mech. Eng. AMD-Vol. 116, 51.Google Scholar
- Scruby, C.B., R.J. Dewhurst, D.A. Hutchings and S.B. Palmer, 1982, Laser Generation of Ultrasound in Metals, in: Research Techniques in Nondestructive Testing, Vol. V, ed. R.S. Sharpe (Academic, New York).Google Scholar
- van der Hijden, 1987, Propagation of Transient Elastic Waves in Stratified Anisotropic Media (North Holland, Amsterdam).Google Scholar
- Wesner, J., K.U. Wurz, K. Hillmann and W. Grill, 1992, Imaging of Coherent Phonons, in: 7th Int. Conf. on Phonon Scattering in Condensed Matter.Google Scholar