Tunable reflected group delay from the graphene/hBN heterostructure at infrared frequencies

In this paper, we theoretically investigated the reflected group delay from the graphene/hexagonal boron nitride (hBN) heterostructure in the infrared band. Since the significant Lorentz resonance characteristic of the dielectric constant of hBN in the bands of near 7.28 mu m and 12.72 mu m, the new graphene/hBN heterostructure is used to realize flexible switching of reflected group delay by the Lorentz resonance mechanism. It is shown that the reflected group delay can be effectively enhanced by tuning the Fermi energy or the number of graphene layers. Moreover, the reflected group delay can be tuned positive or negative depending on the hBN thickness or incident angle. These results will be useful for design of graphene-based optical delay devices in the infrared band.