Plasmonic lattice solitons in nonlinear graphene sheet arrays

Tunable Optical Bistability, Tristability and Multistability in Arrays of Graphene

The optical bistability, tristability and multistability are explored in arrays of graphene. The arrays are periodically arranged spatially by single sheets of graphene. Optical bistability could be achieved with a strong enough incident intensity of light wave. The thresholds of optical bistability and the intervals between the upper and lower thresholds change with the surface conductivity of graphene and the incident wavelength. By increasing the intensity of incident light, tristability and multistability can be induced as well. Furthermore, the thresholds of bistability, tristability and multistability can be regulated via the chemical potential of graphene. This study may have potential applications in optical logic gates, all-optical switches and photomemory.

Surface vector plasmonic lattice solitons in semi-infinite graphene-pair arrays

We investigate the surface vector plasmonic lattice solitons (PLSs) in semi-infinite graphene-pair arrays (GPAs). The surface vector PLSs are composed of two components which are associated with different band gaps. Both components undergo mutual self-trapping at the boundary of the semi-infinite structure when the self-focusing nonlinearity of graphene and the light diffraction reach a balance. Thanks to the strong confinement of SPPs, the surface vector PLSs can be squeezed into a deep-subwavelength width of ~0.003λ. By comparing with bulk solitons, the surface PLSs are more readily to excite by external waves and more sensitive to the surrounding environment. The study may develop promising applications in all-optical switching devices and optical sensors on deep-subwavelength scale.

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.

Vector plasmonic lattice solitons in nonlinear graphene-pair arrays

We investigate the vector plasmonic lattice solitons (PLSs) in nonlinear graphene-pair arrays (GPAs) consisting of periodically arranged double graphene sheets, which are spatially separated. There are two dispersion bands for the Bloch modes in the array due to the coupling of surface plasmon polaritons (SPPs) between the graphene pairs. The vector PLSs composed of two components originate from the nonlinear interaction of Bloch modes in different bands. Both components undergo mutual self-trapping through the balance between diffraction and self-focusing nonlinearity of graphene. Thanks to the strong confinement of SPPs, the vector PLSs can be squeezed into a lateral width of ∼λ/100. The study provides a promising approach to all-optical control on a deep-subwavelength scale.