Symmetric Plasmonic Slot Waveguides with a Nonlinear Dielectric Core: Bifurcations, Size Effects, and Higher Order Modes

Abstract

International audienceWe study the nonlinear stationary waves propagating in metal slot waveguides with a Kerr-type dielectric core. We develop two independent semi-analytical models to describe these waves in 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 higher order modes which are grouped in two families. In addition, we study the influence of the slot width on the first symmetric and asymmetric modes. We also 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. Using realistic values for the optogeometric parameters of the structure, we are able to obtain the bifurcation at a realistic power

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

“…The nonlinear Kerr-type dielectric is isotropic with ϵ core ϵ l;core αjE x j 2 (ϵ l;core being the linear part of the core permittivity and E x being the x component of the electric field), and with α > 0 (focusing nonlinearity). This approximation of the Kerr nonlinearity, taking into account only the transverse component of the electric field, has already been used in models of the NPSWs [6,12]. It allows us to use the fixed power algorithm in the finite element method (FEM) to compute the nonlinear stationary solutions and their nonlinear dispersion curves [13][14][15][16].…”

“…Finally, we describe the stability properties of the main stationary solutions using nonlinear FDTD simulations. © 2016 Optical Society of America 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][2][3][4][5][6]. Several applications have already been proposed for NPSWs [7,8].…”

“…1. Compared to the already studied simple NPSW made of a nonlinear dielectric core surrounded by two semi-infinite metal regions [1,2,6], the improved structure contains additional linear dielectric layers between the core and the metal regions. In this study, we will only consider the symmetric structures even if the asymmetric simple NPSWs have already been considered [12].…”

“…To compute the linear and nonlinear modes we use our custom-built FEM developed to study scalar and vector models for waveguides including nonlinear ones with Kerr regions like microstructured optical fibers and NPSWs [15][16][17]. In this study, ϵ l;core 3.46 2 i10 −4 and n 2 1:10 −17 m 2 ∕W corresponding to amorphous hydrogenated silicon [6], and ϵ met −90 i10 corresponding to gold at 1.55 μm, the wavelength for which all the simulations are done. Losses will be estimated using the method based on the field profiles and permittivity of the imaginary parts described in [3,10,12,18].…”

Loss-compensated nonlinear modes and symmetry breaking in amplifying metal-dielectric-metal plasmonic couplers

“…If plasmons-collective oscillations of electrons-are coupled to the electromagnetic field nearby the surface of a metal, exponentially localized surface plasmon polariton (SPP) modes can be excited [1], SPPs can confine light in the subwavelength scale overcoming the natural limit of light diffraction and are used as optical interconnects in highly integrated optoelectronic circuits [2], In addition, they are responsible for several effects including extraordinary optical transmission through subwavelength hole arrays [3], perfect imaging [4], and giant enhancement of local fields [5], In particular, the latter mechanism boosts all the nonlinear processes [6], which can be exploited in several applications, e.g., biosensing [7], ultrafast processing of optical signals [8], and plasmon-soliton formation [9][10][11], Besides, nonlinearity can be exploited to achieve symmetry breaking and switching in plasmonic arrays and couplers, thus enabling all-optical control and manipulation of SPPs [12][13][14][15][16][17], However, the above mentioned applications are hampered by the presence of large intrinsic ohmic losses of metals that damp the optical signal [18]. In turn, several strategies have been proposed to retain the subwavelength localization provided by SPPs and overcome the loss barrier of metals, e.g., the suppression of interband absorption through ultrashort self-induced trans mitted plasmon solitons [19].…”