Nonreciprocal terahertz beam steering based on magneto-optic metagratings

In this work, an active nonreciprocal THz beam steering has been proposed based on a transversely magnetized metal/InSb metagrating. The nonreciprocal dispersion relation and phase shift characteristics of the metal/InSb waveguide are investigated in details. A metagrating structure with gradient phase shift has been designed based on the metal/InSb waveguide. Under the external magnetic field (EMF), the THz beam can be changed among 0, +1^st, and -1^st order of the metagrating. Due to the nonreciprocity of the metal/InSb metagrating, the deflection angle can be controlled by changing the positive and negative directions of the EMF, to realize bilateral symmetric scanning from -67.8° to 67.8° with over 70% diffraction efficiency, and this device also exhibits the nonreciprocal one-way transmission as an isolator with the isolation of 13 dB. This low-loss, large deflection degree, nonreciprocal beam scanner has a great potential application in the THz regime.