Nonlinear Surface Plasmon Polaritons Research Articles

Propagation and excitation properties of nonlinear surface plasmon polaritons in a rectangular barrier

We propose a scheme to study the nonlinear propagation properties of nonlinear surface plasmon polaritons (SPPs) in a three level $\Lambda$ type electromagnetically induced transparency (EIT) system with modulation of a rectangular barrier. Based on the multi scale method, the nonlinear Schr\"odinger equation (NLSE) describing nonlinear propagation of SPPs is derived, and the rectangular barrier affecting propagation of nonlinear SPPs is provided by an off-resonance Stark field. For the single nonlinear SPPs incident case, by adjusting the height and half width of the barrier, we can realize transmission, trapping and reflection of the nonlinear SPPs. For two nonlinear SPPs symmetrical incident case, we find that a periodic intensity distribution in transverse direction mode can be excited in the rectangular barrier, and we study the relationship between propagation properties of such excited modes in the barrier with nonlinearity, half width of the barrier and phase difference of the initial nonlinear SPPs. In addition, we design an optical switch of nonlinear SPPs based on the above results. The results obtained here not only provide a theoretical basis for the study of the interaction between nonlinear SPPs and external potentials, but also have broad application prospects in the field of optical information at micro/nano scale.

Surface plasmonic Cherenkov radiation and symmetry breaking within a coherent nonlinear nanostructure

Nonlinear conversions within the plasmonic structures are important for ultrafast nanophotonics; however, the impact of higher-order dispersion on nonlinear polaritonic efficiency remains unexplored. In this work, we uncover the role of higher-order dispersion and self-steepening on nonlinear surface-plasmon polaritons (NSPPs) within a coherent plasmonic interface that comprises an atomic medium doped on top of a low-loss negative-index metamaterial (NIMM) layer. This dispersion in the atomic medium--NIMM interface yields nonlinear plasmonic phase match and resonant launching of Cherenkov SPPs. We establish time-reversal and $\mathcal{PT}$ symmetry breaking for propagated NSPPs that yield asymmetric plasmonic comb excitation and anomalous plasmonic phase singularities. Our work thereby suggests a fingerprint for nonlinear plasmonic field evolution through the appearance of a Cherenkov field and develops a framework for designing a frequency selector and nanoscopic pulse shaper, which opens prospects for nonlinear nanophotonic applications.

Nonlocal and Nonlinear Surface Plasmon Polaritons and Optical Spatial Solitons Induced by the Thermocapillary Effect.

We study the propagation of surface plasmon polaritons (SPPs) on a metal surface which hosts a thin film of a liquid dielectric. The Ohmic losses that are inherently present due to the coupling of SPPs to conductors' electron plasma, induce temperature gradients and fluid deformation driven by the thermocapillary effect, which lead to a nonlinear and nonlocal change of the effective dielectric constant. The latter extends beyond the regions of highest optical intensity and constitutes a novel thermally self-induced mechanism that affects the propagation of the SPPs. We derive the nonlinear and nonlocal Schrödinger equation that describes propagation of low intensity SPP beams, and show analytically and numerically that it supports a novel optical spatial soliton excitation.

Optical bistability induced by nonlinear surface plasmon polaritons in graphene in terahertz regime

We demonstrate optical bistability in a prism-air-graphene-dielectric structure. Under a moderate electric field in the terahertz frequency regime, the third order nonlinear optical conductivity is comparable to the linear conductivity. The nonlinear conductivity enhances the energy of surface plasmon polaritons. Both the energy and frequency of the surface plasmon polaritons depend on the strength of the nonlinear current in the graphene layer. When considering excitation in the Kretschmann configuration, the reflectance as a function of frequency exhibits bistability. The origin of the bistability is the field dependence of the plasmon mode. We have determined the parameter regime for the occurrence of bistability in this structure.

Amplification of surface plasmon polaritons in nonlinear medium with full saturation susceptibility model

In this paper, a numerical analysis to model the amplification of nonlinear surface plasmon polaritons (SPPs) propagating along a metal active dielectric interface is presented. Nonlinearity of the medium with gain is considered through the full saturation susceptibility parameter of a two-level model. Above the linear threshold of the gain and loss balance, the nonlinear performance of the amplified SPPs is verified, which agrees well with the experimental results reported in the literature. An important feature of the proposed method is to predict an abrupt increase in output intensity due to amplified spontaneous emission.

Nonlinear Surface Plasmon Polaritons at the Interfaces Between Isotropic Media and Anisotropic Left-Handed Materials

Linear and nonlinear surface plasmon polaritons propagating along the interfaces between isotropic media and uniaxially anisotropic left-handed materials are investigated. A transition layer sandwiched between the connected media is described using a model of a two-dimensional gas of semiconductor quantum dots. The conditions of the existence of surface TM-modes when the components of the permittivity and permeability tensors of the anisotropic left-handed materials are simultaneously negative are determined. Explicit analytical expressions for a surface optical two- dimensional soliton of self-induced transparency in the presence of single and biexciton transitions are given. Numerical simulations for surface solitons are given for different layered systems. It is shown that the total energy flow of the surface solitons depends on the parameters of the quantum dots and the connected media.

Nonlinear TM-polarized waves in non-kerr media

Both the dispersion relation and the guided power flow for nonlinear TM-polarized guided waves have been derived. These guided waves are allowed to propagate down a configuration where a linear film is sandwiched between two rather general nonlinear media as well as down a single interface that separates two nonlinear media. The analytical results have been found using first integrals of the wave equation instead of their explicit solutions. The power flow dependence of the propagation constant in saturable media is discussed numerically, for the cases of nonlinear surface plasmon polaritons and nonlinear surface polaritons as well as for long- and short-range surface plasmon polaritons.