Here had been analyzed the coupling of microring resonators in the presence of Kerr effect. The effects of nonlinear
coupling on optical bistability of microring resonators are investigated too. This result provides a technique to designing
an "all-optical flip-flop circuit".
As the semiconductor materials have strong nonlinear optical effects, they have a great deal of attention in ultrafast alloptical
data processing. In semiconductors, the free carriers (FC) density change with field intensity in process of Two
Photon Absorption (TPA), and leads to second order intensity dependant in refractive index and loss. In this paper, in
addition to Kerr effect, the nonlinear optical effects (TPA) and free carriers is studied theoretically in nonlinear
directional couplers by starting from Maxwell's equations and perturbation method. As results show that TPA and FC
limit the field transmission between waveguides stronger than Kerr effect and the threshold of filed intensity decreases
one order of magnitude. This phenomenon has important applications in switching operation when coupling and
decoupling optical wave is needed.