Surface-induced nonlinearity enhancement in subwavelength rod waveguides

Abstract

We develop a perturbative theory to describe optical propagation in subwavelength rod waveguides. In this approach, we account for loss and nonlinearity in the boundary conditions. A comparison to the traditional perturbative approach used in optical fibers reveals that the surface contribution provides a significant nonlinearity enhancement in the subwavelength regime. We further compare the nonlinearity enhancement of metallic, dielectric, and semiconductor waveguides, in addition to determining the attenuation coefficient of metallic nanowires.

Polariton excitation in epsilon-near-zero slabs: Transient trapping of slow light

“…This can be grasped by expanding both sides of Eq. (8) in Taylor series of ǫ (since |ǫ(Ω)| ≪ 1); at the zeroth order we readily obtain e −kxL = −Θ which is not consistent if Θ = 1 (and which, on the other hand, yields k x = 0 for Θ = −1).…”

Nonlinear graphene plasmonics: Amplitude equation for surface plasmons

“…Allowing for light intensity corrections to the surface current and to the susceptibility of dielectrics surrounding graphene, as well as introducing diffraction due to a finite beam width in the unbound (y) direction, we develop asymptotic expansion of Maxwell equations and boundary conditions to obtain an amplitude equation for quasi-TM and quasi-TE surface waves. The asymptotic expansion procedure is similar to that recently developed for semiconductor and metal nano-waveguides [16,17]. Further, we analyze the relative contribution from dielectrics and graphene to the overall effective nonlinearity of the system for the two types of plasmons, and the impact of geometry on the nonlinearity enhancement.…”

Nonlinear coupled-mode theory for periodic waveguides and metamaterials with loss and gain

“…[3] involved a multi-step procedure of the perturbation series expansion, and such derivation was specific to a planar geometry. Recently, the perturbation analysis was applied to the case of circular rod waveguides [2], however a consideration of more complicated geometries remained an open problem. With our method, it becomes possible to systematically formulate the coupled-mode equations according to Eq.…”

“…In particular, nonlinear optical interactions can be enhanced due to a strong field concentration at metal interfaces [1,2], which may lead to spatial beam self-focusing [3,4]. New regimes of nonlinear wave mixing between forward and backward waves can be efficiently realized in negativeindex metamaterials [5,6,7].…”

“…However, a rigorous derivation of such equations for nonlinear metaldielectric structures, taking into account the effect of metal loss and possible gain in dielectric, has shown that effective nonlinear response can become complex due to the presence of loss [3]. Such rigorous analysis was so far performed only for several simple geometries of planar and circular plasmonic waveguides admitting analytical expressions for the mode profiles [3,1,4,2].…”