Tunable Optical Bistability and Tristability in Nonlinear Graphene-Wrapped Nanospheres

We develop the nonlinear electromagnetic theory (NET) including the self-consistent mean-field approach to investigate the optical multistability of graphene-wrapped dielectric nanoparticles. We demonstrate the optical bistability (OB) of the graphene-wrapped nanoparticle in both near-field and far-field spectra due to electric dipolar modes for small sizes, as predicted in the quasistatic limit (QL). For small sizes, two OB regions can be observed when the magnetic dipolar modes arise under the strong field. On the other hand, for large sizes, one observes the optical tristability (OT) and even optical multistability arising from the contributions of higher-order magnetic modes. Furthermore, both the optically stable region and the switching threshold values can be tuned by changing either the Fermi level or the size of the nanoparticles. Our results show promise for the graphene-wrapped dielectric nanoparticle as a candidate for multistate optical switching, optical memories, and relevant optoelectronic devices.