Proceedings Article | 1 May 2012
Proc. SPIE. 8424, Nanophotonics IV
KEYWORDS: Plasmonics, Plasmonic waveguides, Switches, Switching, Thermal optics, Waveguides, Silicon, Wave propagation, Brain-machine interfaces, Tolerancing
We present a thorough numerical investigation of end-fire coupling between dielectric-loaded surface plasmon
polariton (DLSPP) and compact rib/wire silicon-on-insulator (SOI) waveguides. Simulations are based on the
three-dimensional vector finite element method. The interface geometrical parameters leading to optimum performance,
i.e., maximum coupling efficiency or, equivalently, minimum insertion loss (IL), are identified. We
show that coupling efficiencies as high as 85 % are possible. In addition, we quantify the fabrication tolerances
about the optimum parameter values. In the same context, we assess the effect of a metallic stripe gap and
that of a horizontal offset between waveguides on insertion loss. Finally, we demonstrate that by benefiting
form the low-loss coupling between the two waveguides, hybrid silicon-plasmonic 2 x 2 thermo-optic switching
elements can outperform their all-plasmonic counterparts in terms of IL. Specifically, we examine two hybrid
SOI-DLSPP switching elements, namely, a Mach-Zehnder Interferometer (MZI) and a Multi-Mode-Interference
(MMI) switch. In particular, in the MZI case the IL improvement compared to the all-plasmonic counterpart
is 4.5 dB. Moreover, the proposed hybrid components maintain the high extinction ratio, small footprint, and
efficient tuning traits of plasmonic technology.
