Coupling mode-based nanophotonic U-shaped circuit devices is proposed. Furthermore, the coupling of TM mode between adjacent air channels on metal and propagation of surface plasmon polariton (SPP) waves was demonstrated. Different output intensities were derived by modifying the U-shaped air channel width, and the binary logical value "1" or "0" is obtained after definition of threshold. A spacial coupling mode theory is used to explain the computational simulation results. The theory and the numerical results are well fitted to each other. The structure can be used to obtain all four binary arrays applying to the highly integrated optical circuit.
