arXiv subjects

Wiktor Walasik

Publications and source records attributed to Wiktor Walasik.

23 records · Page 2Linked to original sources

arXiv2015

Nonlinear parity-time-symmetric transition in finite-size optical couplers

Parity-time-symmetric ($\mathcal{PT}$-symmetric) optical waveguide couplers offer a great potential for future applications in integrated optics. Studies of nonlinear $\mathcal{PT}$-symmetric couplers present new possibilities for ultracompact configurable all-optical signal processing. Here, we predict nonlinearly triggered transition from a full to a broken $\mathcal{PT}$-symmetric regime in finite-size systems described by smooth permittivity profiles and, in particular, in a conventional discrete waveguide directional coupler configuration with a rectangular permittivity profile. These results suggest a practical route for experimental realization of such systems.

physics.optics↗

arXiv2015

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.

physics.optics↗

arXiv2015

Plasmon-soliton waves in planar slot waveguides: II. Results for stationary waves and stability analysis

We describe the results of the two methods we developed to calculate the stationary nonlinear solutions in one-dimensional plasmonic slot waveguides made of a finite-thickness nonlinear dielectric core surrounded by metal regions. These two methods are described in detail in the preceding article [Walasik et al., submitted]. For symmetric waveguides, we provide the nonlinear dispersion curves obtained using the two methods and compare them. We describe the well known low-order modes and the higher-modes that were not described before. All the modes are classified into two families: modes with and without nodes. We also compare nonlinear modes with nodes with the linear modes in similar linear slot waveguides with a homogeneous core. We recover the symmetry breaking Hopf bifurcation of the first symmetric nonlinear mode toward an asymmetric mode and we show that one of the higher modes also exhibits a bifurcation. We study the behavior of the bifurcation of the fundamental mode as a function of the permittivities of a metal and a nonlinear core. We demonstrate that the bifurcation can be obtained at low power levels in structures with optimized parameters. Moreover, we provide the dispersion curves for asymmetric nonlinear slot waveguides. Finally, we give results concerning the stability of the fundamental symmetric mode and the asymmetric mode that bifurcates from it using both theoretical argument and numerical propagation simulations from two different full-vector methods. We investigate also the stability properties of the first antisymmetric mode using our two numerical propagation methods.

physics.optics↗

arXiv2014

Symmetric metal slot waveguides with nonlinear dielectric core: bifurcations, size effects, and higher order modes

We study the nonlinear waves propagating in metal slot waveguides with a Kerr-type dielectric core. We develop two independent semi-analytical models to describe the properties of such waveguides. Using those models we compute the dispersion curves for the first ten modes of a nonlinear slot waveguide. For symmetric waveguides we find symmetric, antisymmetric, and asymmetric modes which are grouped in two families. In addition, we study the influence of the slot width on the first symmetric and asymmetric modes, and we show that the dispersion curve of the first asymmetric mode is invariant with respect to the slot width for high propagation constant values and we provide analytical approximations of this curve.

physics.optics↗

arXiv2013

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.

physics.optics↗