Abstract
The numerical analysis of finite planar metal-insulator-metal waveguide structures using the transfer-matrix formalism reveals both bound and leaky surface plasmon (SP) modes. The dispersion relations, propagation lengths and confinement factors of these SP modes are presented. The highest energy SP mode consists of non-radiative (bound) and radiative (leaky) portions separated by a spectral gap. The leaky regime is further divided into antenna and reactive mode regions. The antenna mode may be used for both free-space coupling and beam steering devices.
Highlights
Surface plasmons (SPs), the transverse magnetic (TM) waves propagating along metaldielectric interfaces with fields exponentially decaying in both media, have been extensively investigated for decades
Long-range surface plasmon (SP) waveguides based on thin metal films or stripes (referred to as insulator-metal-insulator (IMI) waveguides) have been studied previously [1,2], but metal-insulator-metal (MIM) SP waveguides offer higher confinement factors and closer spacing to adjacent waveguides or structures[3,4] and have been proposed for this and other potential applications [5,6,7,8]
Analysis of the complete surface plasmon mode set dispersion relations for a finite planar MIM structure with empirical Drude-Lorentz metal parameters has been presented in this paper
Summary
Surface plasmons (SPs), the transverse magnetic (TM) waves propagating along metaldielectric interfaces with fields exponentially decaying in both media, have been extensively investigated for decades. We use an empirical fit of the metal dielectric function to experimental data This results in one notable difference compared to use of a free-electron model; instead of asymptotically approaching resonance frequencies, the dispersion curves cross and form quasibound (QB) modes [15]. The modal symmetry properties (either symmetric-S or antisymmetricA) used to label the modes in this paper are defined by the symmetry of the tangential magnetic field with respect to the waveguide median plane This description differs from other literature definitions usually based on the tangential electric field in propagation direction. 10-9 against previously published results for lossless and lossy bound and leaky waveguides as well as plasmonic waveguides [3,16,17]
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