Asymmetric plasmonic supermodes in nonlinear graphene multilayers

We investigate the nonlinear supermodes of surface plasmon polaritons in graphene multilayers with arbitrary number of graphene layers. Apart from the symmetric and anti-symmetric supermodes which exist in linear multilayer graphene waveguides, more asymmetric supermodes emerge in the nonlinear counterparts as the field symmetry is broken. The number of asymmetric supermodes relies largely on the layer number of graphene. There is a certain threshold of field intensity for the emergence of each individual asymmetric supermode. The threshold increases as the incident wavelength or chemical potential of graphene increases. The study may find applications in building all-optical mode converters and switches.