Tunable multiple soliton generation in Kerr media

摘要

Optical solitons are self-confined robust beams existing in various kind of nonlinear media; their studies are of fundamental as well as technological relevance. The generation of multiple solitons has been studied using modulational instability [1], or from shock waves emerging from either bright or dark input beams propagating in dispersive media [2–5]. We propose a novel route for the generation of multiple solitons using a broad beam launched into a nonlinear medium with a modified distribution of the linear refractive index, i.e. a defect. When the size of the input beam is large compared with the defect width, defect induced modulation in the phase of the beam will result in the formation of multiple fringes. These fringes can evolve into multiple interacting solitons depending on beam excitation level. The number of fringes can be controlled by the height of the defect (i.e. index jump) as well as the ratio between the widths of the beam and of the defect. We solve the one-dimensional normalized Nonlinear Schrödinger Equation of the form equation for an input beam u(X,Z = 0) = Nu0sech(uoX), where Veff (X,Z) = − [nL²(X,Z) + 2n0nL(X,Z)], nL(X,Z) is the linear index profile, k0 = 2π/λ is the vacuum wavenumber (λ is the vacuum wavelength), p = k0²wp²/2, wp is the width of the defect, equation is the normalized field, N is an integer, A is the electric field amplitude, n2 is the Kerr coefficient and n0 is the linear refractive index for the carrier; we also define the normalized coordinates Z = z/Ld (Ld = k0wp²n0) and X = x/wp