Ring-like solitons in plasmonic fiber waveguides composed of metal-dielectric multilayers

We design a plasmonic fiber waveguide (PFW) composed of coaxial cylindrical metal-dielectric multilayers in nanoscale, and constitute the corresponding dynamical equations describing the propagation modes in the PFW with the Kerr nonlinearity in the dielectric layers. The physics is connected to the discrete matrix nonlinear Schrödinger equations, from which the highly confined ring-like solitons in scale of subwavelength are found both for the visible lights and the near-infrared lights in the self-defocusing condition. Moreover, when increasing the intensity of the input light the confinement can be further improved due to the cylindrical symmetry of the PFW, which means both the width and the radius of the ring are reduced.