Demonstration of an all-optical 2-bit digital-to-analog converter based on photonic crystal waveguides

In this article, what we believe to be a new all-optical 2-bit digital-to-analog converter (AODAC) is proposed based on the principle of beam interference in a photonic crystal structure. It is numerically investigated and analyzed by the finite difference time domain (FDTD) method. The proposed AODAC will be realized with eleven optical waveguides and eleven point defects in a square lattice of silicon dielectric rods surrounded in air. The proposed AODAC converts the discrete optical digital signals in the input ports into optical analog signals in the output port. Unlike previous structures, the main advantage of this converter is that input powers as low as 0.5, 1, and 1.5 mW are sufficient for its operation, since no nonlinear rods are included. In addition, its maximum absolute error percentage and maximum insertion loss are obtained as 4.05% and -11.67 dB, respectively.