Acousto-optics science deals with the interaction between sound and light waves. Acousto-optic waves are most important in transferring signals through the communication systems, since modulating signals takes a great advantages in the field of communication engineering, bio-medical, laser beam deflection and laser intensity modulation. The aim of this work is to simulate the fundamentals of an Acousto-Optic Modulator. The simulation procedure is based on theoretical and computational relationships describing acousto-optic properties for three selected materials which are “Glass, Germanium, and Tellurium-Oxide”. Two computer programs have been written using “MATLAB” software, the first used to verify the normalized intensity of the diffracted orders versus peak phase delay using partial differential equation, while the second program is used to study the normalized intensity of the electric field versus time wave propagation and electro-magnetic wave propagation in x, y and z directions, using Finite Difference Time Domain. The results for Glass and Tellurium-Oxide materials shows that the periodic exchange of the normalized intensity between the zero and first orders becomes smaller as the interaction length D increase, this indicate that the higher orders may appear very clear in these materials. The results for the Glass material show that the normalized intensity of the electric field increases with increasing electromagnetic wave propagation in x, y and z directions.The results for Germanium shows that the peak intensity exchange for the zero diffracted order vanish quickly and coincidence with the higher diffracted order