Nonlinear PBG Structures for All-Optical Signal Processing

In our work, we consider theoretically and experimentally (Ge-Se structures) the photonic bandgap (PBG) systems containing nonlinear insertions for possible applications in all-optical adders and logical gates. The principal schemes of an all-optical adder based on pure one-dimensional and combined 1D-3D (or 2D) PBG materials containing optically nonlinear layers are discussed. The photonic structure behavior with changing intensity is investigated for a few systems consisting of a periodically layered structure covered with an optically nonlinear material and theoretical estimations of the logical gate parameters are made for linear 1D Ge-Se photonic crystal covered with the nonlinear doped glass. Also, the results for 2D linear Ge-Se photonic structure are discussed. It is shown that the beam angular-frequency diagrams contain extremely sensitive areas inside the total reflection range, where the weak nonlinearity leads to dramatic change in light reflection and transmission. Both solitary local modes and pure band modes are considered theoretically.