Focusing of acoustic energy at the conical point in zinc

This paper reports observations of the intense focusing of acoustic energy that occurs along the symmetry axis in a zinc single crystal. The focusing is associated with a conical point in the wave surface and thereby the phenomenon of external conical refraction. Our observations have been obtained with (i) pointlike piezoelectric transducers (PZT) as source and detector, (ii) a focused pulsed laser source and small PZT detector, and (iii) a breaking capillary source and capacitive detector at epicenter.