Internal diffraction of ultrasound in crystals: Phonon focusing at long wavelengths.

摘要: We have obtained images of acoustic energy flux in anisotropic media by an ultrasonic analog to ballistic-phonon imaging. The observed reveals a phonon-focusing pattern modulated interference fringes, accord with prior theoretical predictions. While phonon imaging is largely restricted insulators at low temperatures, the technique works ambient temperatures and also applicable metals even noncrystalline materials