Compression of Acoustic Beams at Conversion Reflection in Hexagonal Crystals

It is shown how the entire energy of an acoustic beam incident on a boundary of a hexagonal crystal can be directed into a narrow reflected beam propagating at a small angle to the surface. This process is accompanied by mode conversion: the incident and reflected beams belong to different acoustic branches. The conversion near the total internal reflection is implemented by matching the orientations of the sagittal plane and surface and thereby eliminating the loss for parasitic wave reflection. The found conversion conditions and resonant reflection parameters are expressed in terms of the moduli of elasticity of crystal.