Self-trapping of optical solitons in double Josephson junctions formed by spatially coupled soliton and surface-plasmons

Transfer of population between a surface plasmon excitation on a metal surface and a spatially coupled optical soliton in a nonlinear dielectric waveguide bears similarities to the transition dynamics of a Josephson junction... [ view full abstract ]

Transfer of population between a surface plasmon excitation on a metal surface and a spatially coupled optical soliton in a nonlinear dielectric waveguide bears similarities to the transition dynamics of a Josephson junction in three-level Bose-Einstein condensates, which demonstrates that a photonic Josephson junction, in which a Kerr-type nonlinearity is sandwiched between cascaded dielectric and metal layers on both sides, can be obtained through a surface plasmon-soliton-surface plasmon coupled optical system. The nonlinear coupling that inherently depends on the population imbalance of the levels is the driving parameter of this type of transition. The physics behind the transition dynamics in both numerical and analytical investigative basis reveals a well-known quantum mechanical phenomenon: macroscopic self-trapping of soliton state. This phenomenon is based on a quantum theory of light propagation in a system of two optical waveguides in which tunneling is enabled by a common continuum of modes coupled to both optical channels. For classical light waves, the emergence of a trapped state placed in the continuum is caused by Fano interference between different light leakage channels. This paper claims that plasmonic structures originally designed to mimic the quantum mechanical phenomena, may exhibit themselves as proper analogues of macroscopic quantum self-trapping. Transfer of population between three states results periodic behavior caused by the dissipationless characteristics of the system. However, the system can be configured into a particular state, in which the soliton amplitude oscillations can be suppressed into stationary soliton propagation, so that the soliton channel becomes a dark state between two surface plasmons, which otherwise couldn’t affect one another. This phenomenon can be obtained for a large combination of system parameters, as well as the initial surface plasmon and the soliton amplitudes within the physical limitations. The conditions that yield the self-trapping are discussed along with the realistic parameters for experimental realization.