Due to a strong enhancement of the field induced by the excitation of surface plasmon polaritons and increased optical nonlinearity, surface plasmons can be employed for realization of a variety of nonlinear optical effects. In particular, several nonlinear optical processes have been demonstrated in plasmonic nanostructures, e.g., optical limiting and self-phase modulation in arrays of structured nanoparticles or second-harmonic generation in nanostructured metal films. In addition, strong geometrical confinement can boost the efficiency of nonlinear optical effects, including the generation of subwavelength solitons in metal-dielectric multilayers and arrays of metal nanowires. The solitons supported by such media result from a balance between tunneling of surface plasmon modes and nonlinear self-trapping.
In our work, we suggest and study a novel class of nonlinear effects in arrays of subwavelength metallic nanoparticles. More specifically, we focus on two fundamental nonlinear phenomena: (i) bistability and (ii) modulational instability. We demonstrate that a bistable nonlinear response of each nanoparticle in the array can lead to the formation of a novel type of nonlinear localized modes---plasmonic kinks, which describe switching waves connecting two different states of polarization of metallic nanoparticles. Such plasmonic kinks are characterized by a subwavelength extent and tunable (changing from zero to a finite value) velocity. Moreover, two slowly moving kinks of the opposite polarity are able to create a stable bound state which can be regarded as a deeply subwavelength dissipative plasmon soliton.
We also analyze modulational instability in such nanostructures, and describe numerically several scenarios of its development. We show that modulational instability can result in the generation of regular periodic or quasi-periodic modulations of the particle polarizations, and reveal that the arrays of nonlinear metallic nanoparticles can support long-lived standing and moving oscillating nonlinear localized modes which can be termed plasmon oscillons, in analogy with localized modes in driven granular materials and Newtonian fluids.
In our work, we suggest and study a novel class of nonlinear effects in arrays of subwavelength metallic nanoparticles. More specifically, we focus on two fundamental nonlinear phenomena: (i) bistability and (ii) modulational instability. We demonstrate that a bistable nonlinear response of each nanoparticle in the array can lead to the formation of a novel type of nonlinear localized modes---plasmonic kinks, which describe switching waves connecting two different states of polarization of metallic nanoparticles. Such plasmonic kinks are characterized by a subwavelength extent and tunable (changing from zero to a finite value) velocity. Moreover, two slowly moving kinks of the opposite polarity are able to create a stable bound state which can be regarded as a deeply subwavelength dissipative plasmon soliton.
We also analyze modulational instability in such nanostructures, and describe numerically several scenarios of its development. We show that modulational instability can result in the generation of regular periodic or quasi-periodic modulations of the particle polarizations, and reveal that the arrays of nonlinear metallic nanoparticles can support long-lived standing and moving oscillating nonlinear localized modes which can be termed plasmon oscillons, in analogy with localized modes in driven granular materials and Newtonian fluids.
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