Enhancing the nonreciprocal Goos-Hänchen shift by the Fano resonance of coupled gyromagnetic chains at normal incidence.

We report a resonance-enhanced nonreciprocal Goos-Hänchen (GH) shift for the wave reflected from the coupled gyromagnetic chains. We demonstrate that the Fano resonance enhances the GH shift with high reflectivity at normal incidence, and the resonance results from the interference between the leaky guided modes of the coupled chains. Furthermore, we show that the GH shift can be controlled by the number of stacked chains. The Fano resonance-enhanced GH shift offers a new efficiently way to enhance and control the GH shift for reflected wave beam. Such coupled gyromagnetic chains provide an extremely compact way for the devices such as unidirectional couplers and other integration photonic components, paving the way for the applications of nonreciprocal GH shift.