Abstract
A structure for guiding surface plasmon polaritons (SPPs) over millimeter
distances with tight mode confinement is presented and analyzed in detail
using the finite element method. The proposed long-range plasmonic waveguide
consists of a dielectric ridge deposited on a narrow metal stripe supported
by a dielectric buffer layer covering a low-index substrate. It is shown that
such an asymmetric waveguide structure can be designed to support a long-range
symmetric SPP mode, featuring a propagation length of ${\approx} 3.1$ mm and lateral mode width
of ${\approx} 1.6\ \mu$m at telecom wavelengths of ${\sim}
1.55\ \mu$m. Our analysis covers a broad spectrum of parameters:
ridge dimensions, buffer layer parameters (refractive index and thickness),
as well as metal stripe width, considering in detail the underlying mechanisms
of SPP waveguiding in this configuration. The suggested configuration offers
easy connection to electrodes enabling, e.g., thermo-optic or electro-optic
control, and is technologically simple, making fabrication possible using
only a few lithography steps. Additionally, a new figure of merit is introduced,
which is related to a number of plasmonic components allowed for a given mode
confinement and propagation loss, aiming thereby at the evaluation of the
application potential of plasmonic waveguides.
© 2011 IEEE
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