FREQUENCY-CONVERSION OF ELASTIC RADIATION IN ACOUSTICALLY GYROTROPIC CRYSTALS

The characteristics of the generation of elastic radiation at a converted (combination) frequency associated with three-wave interaction in gyrotropic media with quadratic nonlinearity are investigated. It is shown that the presence of acoustical activity imparts ellipticity to waves propagating in a crystal, making it possible for interaction and frequency conversion of the radiation to take place in directions where such phenomena do not occur in nongyrotropic media. It is established that the second harmonic of shear waves can be generated only for crystals of the middle category along and in the vicinity of the acoustic axis, where a low order of tangency of the nappes of the wave-vector surface occurs in the absence of gyrotropy.