Magnetically controllable nonreciprocal Goos-Hanchen shift supported by a magnetic plasmonic gradient metasurface

We demonstrate a magnetically controllable nonreciprocal Goos-Hanchen (GH) shift enabled by the magnetic plasmonic gradient metasurfaces (GMSs) consisting of an array of ferrite rods with a rotation gradient introduced to the rod dimers in the unit cell. The incident Gaussian beam is observed to exhibit an evident GH shift about 5 lambda when it is incident from one side, whereas for the Gaussian beam incident from the geometrically symmetric direction with respect to surface normal only a very small GH shift comes into appearance. The phenomenon arises from the unidirectional coupling of the incident beam with the magnetic plasmonic GMSs due to the time-reversal-symmetry-breaking nature of the magnetic system as evidenced from the photonic band diagrams of the edge states. The unidirectional GH shift can also be implemented at different incident angles by either engineering the gradient of the GMSs or tuning the bias magnetic field. By designing the magnetic plasmonic GMSs with more exquisite configurations we can expect a lot more nonreciprocal properties, adding additional freedom in manipulating electromagnetic waves.