A GROUP OF ANALYTICAL EXPRESSIONS OF THE LIGHT INTENSITIES DIFFRACTED BY ULTRASONIC WAVES

The analytical expressions for the intensities of the light diffracted by ultrasonic waves are derived by means of the normal mode approach under such a limited situation that the incident light is normal to the acoustic waves and only three orders （n=0, n=+1 and n= -1） appear in the aeousto-optical diffraction spectrum. The results are coincident with that given by Nath based on the Ramen-Nath equations. A criterion for the validity of those expressions is obtained by using numerical calculations implemented in the range of 1 ≤ Q ≤10,and it is demonstrated that the expressions will be valid as long as the condition of s=w/Q≤0.3 maintains.