Nano-scale “plasmon-soliton”

Abstract

Formation of novel hybrid vector spatial plasmon-soliton in Kerr slab in-between metal plates is analyzed with a novel NLSE. The soliton self-trapping in lateral dimension is assisted by the plasmonic effect. OCIS codes: (240.6680) Surface Plasmons; (190.5530) Pulse propagation and Solitons;Circuitry downscaling requires new optical toolboxes to play a substantial role in their interconnects. In ordinary optical waveguides the tightest light confinement attainable is λ/2 (λ is wavelength). This limitation can be overcome incorporating metals into the configuration, giving rise to surface plasmon polariton (SPP) [1]. Here we analyze novel configuration where light is transversely tightly guided between two metal sheets, and laterally self trapped by Kerr effect. The plasmonic effect enables overcoming the λ/2 confinement limitation on both transverse and lateral dimensions. Moreover, the implementation of nonlinear self-trapping, rather than ordinary waveguiding, enables for all-optical controlled interconnects, and relaxes the requirement for fabrication of in-plane nanostructures. The very tight field confinement is also instrumental in exhibiting such solitons with small optical powers.To thrive with the plasmon-soliton analysis we derive Non-linear Schrödinger Equation (NLSE) for TM modes guided in the lateral plane, then introduce the plasmonic effect via a metal guiding structure. We could not find any previous analysis based on NLSE for TM modes (solitons) self trapped by Kerr nonlinearity in the lateral (in-plane) dimension of a transverse (vertical) slab waveguide structure. Even though experimental evidence for TE guided modes in such constellation was presented [e.g. 2], most of the analysis was focused on (1+1)D solitons with nonlinearity that modifies the transverse guiding mode profile (or self sustaining in bulk nonlinear media), while invariant in the lateral dimension [e.g. 3,4]. Neither accounted for the 3D vector nature of the guided spatial soliton, and although some incorporated waveguiding effects in the transverse dimension, using a variation method, they neglected the vector nature of field [5].The configuration includes propagation along z axis of CW waves localized in x axis (the transverse dimension) by the waveguide layers and self-trapped by Kerr nonlinearity in y axis (the lateral dimension). We assume that the nonlinearity is weak, thus the mode distribution in x axis is dominated by the linear index profile. For vanishing nonlinearity the structure supports two distinguished mode families: TE and TM comprising different field components {H x ,E y ,H z } and {E x ,H y ,E z } respectively. However, the separation to TE/TM modes relies on the assumption that ∂ y =0, which is false when the nonlinearity sets in, leading to self-trapping in y direction and thus coupling the TE/TM modes. However, TE/TM based analysis in the nonlinear slab is reasonable when the soliton width (∆y) is much larger than the mode width (∆x). Then, the x-axis field distribution enters the y-axis calculation as ...