Nondiffracting Bulk-AcousticXwaves in Crystals

The concept of nondiffracting waves is generalized to encompass bulk-acoustic waves within crystalline media. We introduce acoustic Bessel beams and generalized $X$ waves for anisotropic elastic materials. Detailed numerical predictions for propagation-invariant bulk-acoustic beams of various orders, and also $X$ pulses, are presented for experimental verification. The material parameters used have been chosen appropriately for quartz, the most important material for acoustic device applications.