where n is the variation in the refractive index generated by the
acoustic wave, n0 is the refractive index without acoustic wave, p is
the elasto-optic coefficient, Ps is total acoustic power, is material
density, vs is the acoustic velocity, L and H are the length and height
of rectangular section of transducer, respectively. The value of n
mainly depends on the properties of acousto-optic material and the
strength of acoustic wave.