Ultrahigh-contrast all-optical diodes based on tunable surface plasmon polaritons

We report a strategy for achieving ultrahigh-contrast all-optical diodes by using tunable surface plasmon polaritons (SPPs) in a silver grating coated with poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene], a nonlinear organic material. According to the nonlinear optical Kerr effect, the coupling of SPPs on both sides of the silver grating varied with the pump intensity of incident light, which results in a shift of resonant frequencies of extraordinary transmission modes. The asymmetric configuration and the optical nonlinearity ensure unidirectional transmission properties. An ultrahigh contrast ratio of 2166 is achieved theoretically.