Reconfigurable nonreciprocity with a nonlinear Fano diode

We propose a dynamically tunable nonreciprocal response for wave propagations by employing nonlinear Fano resonances. We demonstrate that the transmission contrast between waves propagating in opposite directions can be controlled by an excitation signal. In particular, the unidirectional transmission can be flipped at different time of a pulse, resembling a Fano diode with dynamical reconfigurable nonreciprocity. The key mechanism is the interaction between a linear and a nonlinear Fano resonance that allows for the tunable unidirectional wave propagation and ultrahigh transmission contrast ratio. We further present a realistic photonic example which demonstrates the properties of nonreciprocity can be dynamically manipulated using a pump pulse, based on the general theoretical model.