Plasmon-soliton waves in planar slot waveguides: I. Modeling

We present two complementary models to study stationary nonlinear solutions in one-dimensional plasmonic slot waveguides made of a finite-thickness nonlinear dielectric core surrounded by metal regions. The considered nonlinearity is of focusing Kerr type. In the first model, it is assumed that the nonlinear term depends only on the transverse component of the electric field and that the nonlinear refractive index change is small compared to the linear part of the refractive index. This first model allows us to describe analytically the field profiles in the whole waveguide using Jacobi elliptic special functions. It also provides a closed analytical formula for the nonlinear dispersion relation. In the second model, the full dependency of the Kerr nonlinearity on the electric field components is taken into account and no assumption is required on the amplitude of the nonlinear term. The disadvantage of this approach is that the field profiles must be computed numerically. Nevertheless analytical constraints are obtained to reduce the parameter space where the solutions of the nonlinear dispersion relations are sought.Comment: 13 pages, 1 figure, see next article part II entitled "Plasmon-soliton waves in planar slot waveguides: II. Results for stationary waves and stability analysis", link: http://arxiv.org/abs/1506.0817

Stationary plasmon-soliton waves in metal-dielectric nonlinear planar structures: modeling and properties

We present three complementary methods to study stationary nonlinear solutions in one-dimensional nonlinear metal-dielectric structures. Two of them use an approximate treatment of the Kerr type nonlinear term taking into account only the leading electric field component, while the third one allows for an exact treatment of the nonlinearity. A direct comparison of the results obtained with all three models is presented and the excellent agreement between them justifies the assumptions that have been used to construct the models. A systematic study of the configurations made of two, three, or four layers, that contain a semi-infinite Kerr type nonlinear dielectric, a metal film and linear dielectrics is presented. Detailed analysis of properties, type and number of solutions in these three types of structures is performed. The parameter ranges where plasmon-soliton waves exist are found. The structures with realistic opto-geometric parameters where plasmon-solitons exist at power levels already used in spatial soliton studies are proposed and studied.Comment: 21 pages, 17 figures, 1 tabl

Improved nonlinear slot waveguides using dielectric buffer layers: properties of TM waves

International audienceWe propose an improved version of the symmetric metal slot waveguides with a Kerr-type nonlinear di-electric core adding linear dielectric buffer layers between the metal regions and the core. Using a finite element method to compute the stationary nonlinear modes, we provide the full phase diagrams of its main TM modes as a function of total power, buffer layer and core thicknesses, that are more complex than the ones of the simple nonlinear metal slot. We show that these modes can exhibit spatial transitions towards specific modes of the new structure as a function of power. We also demonstrate that, for the main modes, the losses are reduced compared to the previous structures, and that they can now decrease with power. Finally, we describe the stability properties of the main stationary solutions using nonlinear FDTD simulations. Nonlinear plasmonic slot waveguides (NPSWs) have drawn attention in the last decade due to the strong light confinement in the nonlinear dielectric core ensured by the surrounding metal regions, and to their peculiar nonlinear effects [1–6]. Several applications have already been proposed for NPSWs [7, 8]. Nevertheless, the experimental observation of plasmon-soliton waves in these NPSWs is still lacking even if linear slot waveg-uides have already been fabricated [9]. Similarly to the case of the single nonlinear dielectric/metal interface structures [10, 11], the modes already studied in the simple NPSWs suffer from high losses that seriously limit the propagation length of the waves. In the present study, we propose and study an improved structure in which buffer linear dielectric layers are added between the nonlinear dielectric core and the two semi-infinite metal regions. The article is organized as follows. First, we describe the model and numerical method we use to study the stationary nonlinear waves in the improved NPSW we propose. Secondly, we describe the linear solutions of the new structures in order to classify the nonlinear solutions. Thirdly, we give the properties of the nonlinear stationary solutions and show that, for some linear parameter configurations, new modal spatial transitions as a function of power occur compared to the simple NPSW case. We provide full phase diagrams for the improved NPSW as a function of total power, buffer layer and core thicknesses. We also prove that the added buffer dielectric layers are able to reduce losses and allow them to decrease with power in most of the cases. Finally, using the FDTD method we study the stability properties of the main nonlinear solutions

Discontinuities in open photonic waveguides: Rigorous 3D modeling with the finite element method

In this paper, a general methodology to study rigorously discontinuities in open waveguides is presented. It relies on a full vector description given by Maxwell's equations in the framework of the finite element method. The discontinuities are not necessarily small perturbations of the initial waveguide and can be very general, such as plasmonic inclusions of arbitrary shapes. The leaky modes of the invariant structure are first computed and then injected as incident fields in the full structure with obstacles using a scattered field approach. The resulting scattered field is finally projected on the modes of the invariant structure making use of their bi-orthogonality. The energy balance is discussed. Finally, the modes of open waveguides periodically structured along the propagation direction are computed. The relevant complex propagation constants are compared to the transmission obtained for a finite number of identical cells. The relevance and complementarity of the two approaches are highlighted on a numerical example encountered in infrared sensing. Open source models allowing to retrieve most of the results of this paper are provided.Comment: The GetDP/Gmsh scripts allowing to retrieve the results are attache

Spatial nonlinearity in anisotropic metamaterial plasmonic slot waveguides

We study the main nonlinear solutions of plasmonic slot waveguides made from an anisotropic metamate-rial core with a positive Kerr-type nonlinearity surrounded by two semi-infinite metal regions. First, we demonstrate that for a highly anisotropic diagonal elliptical core, the bifurcation threshold of the asymmetric mode is reduced from GW/m threshold for the isotropic case to 50 MW/m one indicating a strong enhancement of the spatial nonlinear effects, and that the slope of the dispersion curve of the asymmetric mode stays positive, at least near the bifurcation, suggesting a stable mode. Second, we show that for the hyperbolic case there is no physically meaningful asymmetric mode, and that the sign of the effective nonlinearity can become negative

Effect of cladding geometry on resonant coupling between fundamental and cladding modes in twisted microstructured fibers

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Linear and Nonlinear Characterizations of Chalcogenide Photonic Crystal Fibers

International audienceIn this paper, we investigate the linear and nonlinear properties of GeSbS and AsSe chalcogenide photonic crystal fibers. Through several experimental setups, we have measured the second- and third-order chromatic dispersion, the effective area, losses, birefringence, the nonlinear Kerr coefficient as well as Brillouin and Raman scattering properties