All-optical logic gates based on unidirectional surface plasmon polaritons

Optical logic gates are important elements in optical computing and optical circuits. In this study, all-optical logic gates, including OR, XOR, XNOR, NAND, and NOT gates, are obtained in a composite structure composed of gyroelectric material and metal based on the interference and absorption of surface waves. In the composite structure, a Y-shaped channel through which surface plasmon polaritons propagate unidirectionally is formed. Through the ingenious one-way surface plasmon polaritons, backscattering and side-scattering generated by the composite structure and influencing the surrounding devices are prohibited effectively. The precisely controlled optical phase difference ensures the realization of five different logic gates with high contrast ratios. The maximum contrast ratios for XOR, XNOR, NAND, and NOT gates are 31.64 dB, 43.47 dB, 31.47 dB, and 43.47 dB, respectively. The output logic states “1”or “0” obtained by different logic inputs have nearly the same light intensity. Our research results provide the possibility for constructing all-optical integrated logic devices.