▎ 摘　　要

Light propagation in an asymmetric multilayered structure composed of a linear defective photonic crystal and nonlinear graphene layer is theoretically investigated. A (BA)(4)/graphene/(AB)(4)(AABB)(4) structure with a slight perturbation in the (AABB)(4) part can provide non-reciprocal transmission to achieve an optical diode. This structure was optimized in order to have a low-operation input intensity, high-contrast, small-size all-optical diode without an additional pump signal. In this work, four different passive all-optical diodes are presented. The best contrast ratio is 63, and the minimum operation input intensity for diode action is 2.7 x 10(-3)MW/cm(2) This structure an gives an all-optical diode with a smaller size and higher efficiency in comparison to previous works. (C) 2019 Optical Society of America