Aeoustic transients generated by high voltage pulses in longitudinal KDP modulator crystals were investigated. Photographic method has been developed to visualize the aeoustie waves. The experiments directly demonstrate the piezoeleetric acoustic wave generation, the acoustic wave propagation, the reflexion, diffusion and diffraction of aeoustic waves and the interaction of acoustic waves with crystal imperfections. From the experimental results the velocity of shear waves and the related elastic constant can be evaluated.
IntroduetionFor quantum-e]ectronic applications devices based on the linear eleetrooptic effect [1] are widely used. Crystals having good linear electrooptic properties are usuaIly strongly piezoelectric [2]. An electrie fie]d appl/ed to linear e]ectrooptic crysta]s acts on their refraetive properties by two distinguishable mechanisms. The primary effect is direct interaetion between the electric field and the electrons and optical phonons of the crystals. The mechanical strains caused by the inverse piezoelect¡ effect give secondary contributions to the change of refractive Ÿ by the strain optic effect, which is known as the secondary electrooptic effect.Several papers [3--18] have been published on problems originating from the secondary electrooptic effeet. Sueh problems are, e.g., the separation of the primary from the seeondary effect, the disagreements between the results of different measurements of the linear electrooptie characte¡ of crystals [3--7], and, mainly in the atea of applications, the influence of the seeondary effects on the operation of eleetrooptic deviees [6--18].The origin of these problems essentially lies in the different time-dependenees of the primary and secondary effects. The primary effect follows quasi simultaneousIy the applied eleetrie field. The seeondary-strain-optie eontribution reacts with delay aecording to the inertia and resistanee of the lattiee to mechanieal deformations.
