The contrast improvement of an ultrasound nematic detector by means of an electric-field

In the frame of the continuum theory, the calculation of the hydrodynamic interaction ultrasound-nematic, also in the presence of an electric field, has been carried out. The mean square tilt angle, and consequently, the contrast is shown to be considerably improved, until the electrically controlled birefringence threshold is reached. Experimental measurements of the cell capacitance variations, performed by means of a lock-in amplified bridge method, show the same behavior of the theoretical curve, calculated in some restrictive hypotheses.