All-optical logical gates built on optically linear bandgap structures covered with the nonlinear material

In our work, we investigate photonic bandgap (PBG) structures coated by nonlinear covering as systems that are of interest for possible applications in the all-optical adders and logical gates. Two principal schemes of an all-optical adder based on the ID PBG materials containing optically nonlinear layers are discussed. It is shown that the only nonlinear layer covering linear photonic crystal gives effective signal control and signal processing. Theoretical estimations of the adder cell parameters are made for Si/SiO2 photonic crystals covered with layers made from nonlinear doped glasses. The calculated angular-frequency diagrams exhibited extremely sensitive areas inside the total reflection range, where the weak nonlinearity leads to dramatic change in light reflection and transmission.