SAW second harmonic fields nonlinearly produced by spatially limited beams

A theoretical model of second harmonic wave diffrac- tion in SAW propagation is proposed, which considers each plane wave in the momentum spectrum of the funda- mental wave to generate a second harmonic wave by inte- raction with all the other spectral components: the field is then obtained by the integration of all the partial con- tributions. Second harmonic fields are detected by means of a high resolution phase contrast optical probing tech- nique. Transversal patterns are presented of the second harmonic field produced in yz-LiNbO3 crystals by funda- mental beams of different directivity and a comparison is performed with the theoretical profiles.