ACOUSTIC FIELD ANALYSIS OF SAW BEAMS PARAMETRICALLY GENERATED IN NONLINEAR MIXING PROCESSES.

The generation of a mixed frequency wave by the nonlinear elastic interaction of two fundamental surface acoustic waves is studied through an optical method, that uses a complex filter in the Fourier plane of a slightly varied Abbe imaging system. The nonlinear field is analyzed point by point in transversal cross-secttions and results, obtained on y-z LiNbO3 sample at beating frequencies of 39 and 58 MHz, are compared with a theoretical model, based on the Fourier expansion of the acoustic interacting fields in terms of plane waves.