Dark soliton pairs in fiber couplers

coupler. Due to evanescent coupling, the light pulses launched in the input of the bar channel transfer completely into the cross channel. But when the intensities of light pulses are high, the NLDC is detuned such that there is a change in their refractive index because of the nonlinear effect. At a particular critical power, light pulses would emerge from each waveguide and above the critical power, most of the energies of the light pulses would remain in the bar channel. In NLDCs, thus, the optical switching takes place between the two channels by the change in the intensities of the input light pulses.Switching dynamics of optical (bright) solitons by considering the effects of constant coupling dispersion [8,9], which causes splitting in pulses, higher-order parameters [10-12] and gain and loss [13], etc., have been extensively investigated in NLDCs by researchers after the innovative theoretical work carried out by Jensen [14]. But, in all these works, the NLDC is assumed to be symmetric in all aspects. However, in practice, symmetric fiber couplers are rarely existent. This factor may raise attention on fabricating asymmetric fiber couplers as they are easier to fabricate than the symmetric nonlinear fiber couplers. As explained in Ref. [15], the asymmetry in nonlinear directional couplers can be introduced in many ways. First, in a simple way, the asymmetric fiber couplers can be manufactured by creating a difference in the diameter of the cores. This difference in the diameter of the cores tends to produce not only the phase-velocity mismatch but also a change in the nonlinear coefficients. Second, the asymmetric nature can be obtained by distorting the shape of the cores while maintaining their cross-sectional areas equal. In such birefringent couplers, one can have the asymmetry in the form of phase-velocity mismatch without getting a change in the nonlinear coefficients. Third, to attain the asymmetry, we can use fibers having different dispersion Abstract Switching characteristics of dark soliton in asymmetric nonlinear directional couplers are numerically studied. Every individual effect, responsible for producing asymmetry in nonlinear directional coupler, has been analyzed in detail. It is found that group-velocity mismatch and the difference in group-velocity dispersions between the two cores have no impact on dark soliton, which can be specified as an advancement over the bright solitons. The effects of phase velocity, the difference in effective mode areas and the linear coupling coefficient on the dark soliton switching are also investigated.

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“…In Refs. [25,26], it is shown that dark solitons can propagate and switch between the cores in the normal dispersion regime. In Ref.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of dark soliton switching in asymmetric nonlinear fiber couplers

2015

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“…They occur when kh < 1.363 for water of depth h and waves of wave number k, and the waves correspond approximately to solutions of the DNLSE. The coupling of dark solitons in optical fiber devices has also been considered [8].…”

Section: Introductionmentioning

confidence: 99%

Soliton, rational, and periodic solutions for the infinite hierarchy of defocusing nonlinear Schrödinger equations

Ankiewicz

2016

Phys. Rev. E

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Analysis of short-pulse propagation in positive dispersion media, e.g., in optical fibers and in shallow water, requires assorted high-order derivative terms. We present an infinite-order "dark" hierarchy of equations, starting from the basic defocusing nonlinear Schrödinger equation. We present generalized soliton solutions, plane-wave solutions, and periodic solutions of all orders. We find that "even"-order equations in the set affect phase and "stretching factors" in the solutions, while "odd"-order equations affect the velocities. Hence odd-order equation solutions can be real functions, while even-order equation solutions are complex. There are various applications in optics and water waves.

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“…[2]. Experimentally, DSs were created in various physical systems, including optical fibers [3,4], and BEC [5].DSs exist also in coupled NLS equations, including models of dual-core optical couplers [6]. In the latter context, the inter-core coupling may be dispersive, like the cores themselves [7,8], the effect that was observed experimentally [9].…”

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confidence: 99%

Dark solitons in dual-core waveguides with dispersive coupling

Kartashov

Malomed

2015

Opt. Lett.

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We report on new types of two-component one-dimensional dark solitons (DSs) in a model of a dual-core waveguide with normal group-velocity dispersion and Kerr nonlinearity in both cores, the coupling between which is dispersive too. In the presence of the dispersive coupling, quiescent DSs supported by the zero-frequency background are always gray, being stable with the out-of-phase background, i.e., for opposite signs of the fields in the cores. On the contrary, the background with a nonzero frequency supports quiescent black solitons which may be stable for both out-and in-phase backgrounds, if the dispersive coupling is sufficiently strong. Only DSs supported by the out-of-phase background admit an extension to the case of nonzero phase mismatch between the cores.Dark solitons (DSs) are fundamental modes in media where signs of nonlinear and dispersive terms in the nonlinear Schrödinger (NLS) equation, governing evolution of excitations, are opposite. DSs were predicted in Ref. [1] in the context of the mean-field theory of Bose-Einstein condensates (BECs), and obtained in the framework of the inverse scattering method in Ref. [2]. Experimentally, DSs were created in various physical systems, including optical fibers [3,4], and BEC [5].DSs exist also in coupled NLS equations, including models of dual-core optical couplers [6]. In the latter context, the inter-core coupling may be dispersive, like the cores themselves [7,8], the effect that was observed experimentally [9]. The dispersive coupling introduces new physics, as it links the temporal structure of optical pulses with their energy distribution between the cores, similar to the coupling of the translational and spinor degrees of freedom in spin-orbit-coupled (SOC) BECs [10]. In particular, the interplay of the SOC with the cubic selfattraction of the condensate allows to suppress collapse and leads to formation of stable two-dimensional (2D) bright solitons in the free space [11]. A similar mechanism produces stable families of spatiotemporal optical bright solitons in a dual-core planar waveguides with the Kerr self-focusing acting in each core [12]. SOC in selfrepulsive BECs in optical lattices supports vortex and half-vortex solitons [13]. Similarity of mathematical description of evolution of SOC BEC and light propagation in waveguides with dispersive coupling may allow transfer of many interesting concepts from the field of optics to matter wave systems, and vice versa.DSs in dispersively coupled waveguides were considered recently, mainly from the perspective of the design of switching devices [14,15]. DSs were also studied in SOC-BEC models [16,17], where, unlike in the optical setting, a trap potential is an inherent part of the physically relevant model. In the presence of the trapping potential DSs bifurcate from the first excited state of the potential in the linear limit [18,19]. The respective quiescent DSs represent nonlinear modes with zero intensity at the center [20] (black solitons, BSs).In this Letter, we introduce an essentially new...

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Dark soliton pairs in fiber couplers

Cited by 10 publications

References 10 publications

Numerical investigation of dark soliton switching in asymmetric nonlinear fiber couplers

Numerical investigation of dark soliton switching in asymmetric nonlinear fiber couplers

Soliton, rational, and periodic solutions for the infinite hierarchy of defocusing nonlinear Schrödinger equations

Dark solitons in dual-core waveguides with dispersive coupling

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