Photonic crystals were made on the basis of structure of natural crystals. Almost, all metal elements and most of insulated elements and compound materials are found in the form of crystal at the nature. At such materials, atoms and molecules play scattering role for electron waves. At the present paper, proposed structure of two dimensional photonic crystals having square grid and including silicone circular rods at air background at terahertz extension were studied. Also, electric and magnetic fields were estimated through finite difference method limited at time domain. [1] At this simulation, optic switching was investigated on the basis of photonic crystal structure with one waveguide that the performance of these tools is based on forming faults at photonic crystals affected by Ker nonlinearity.Also optimization was done to increase maximum rate of normalized power of constant state by two parameters including change of silicone cavities and polymer radius. پرونده مقاله