All-optical logic gates based on coupled heterostructure waveguides in two dimensional photonic crystals

In this study, all-optical logic gate with multifunctional performance have been designed in two-dimensional coupled photonic crystal waveguides (CPCWs) employing modulation of the refractive index in the coupling region. A two dimensional finite-difference time domain (2D-FDTD) was employed in our numerical simulations. It is shown that by switching the optical signal to different input waveguide ports, the proposed device can function as AND, OR, NOR and NOT gates operating at many or single wavelength. Our simulation results show that the optimized devices have very good transmission efficiencies, a broad frequency range and the contrast ratios between the output ports reveal a satisfactory level. Our results not only provide a simple on chip platform for next generation logic optical circuits, but also open up the possibility for the realization of ultrahigh speed signal processing, and future photonic crystal based all-optical integrated circuits.