Numerical Modelling of Plasmonic Waveguides

Abstract

Plasmonics play an essential role now in the area of compact on chip optical systems; this is due to their unique characteristics and the ability of guiding light below the diffraction limit. Moreover, the integration between optical systems and electronic systems can be realised using those nanostructures. Since the advent of these devices, there is an urgent need to have an accurate numerical model for plasmonic structures.

Numerical simulations play an important role for the design and modeling of plasmonics. In this thesis, the conventional full vectorial finite difference method (FVFDM) and a nine node based full vectorial finite difference method for linear oblique and curved interfaces (FVFDM-LOCI) are used.

In this dissertation, new plasmonic structures for manipulating light at the nanoscale are explored. The modal analysis of a novel design of three trenched single mode channel plasmon polaritons is introduced and analysed using the full-vectorial finite difference method for linear oblique and curved interfaces. The analysed parameters are the real effective index, propagation length, and lateral mode radius 3db- addition, the figure of merit (FOM), defined as the ratio between propagation length and lateral mode radius, is also studied. The analysis is performed for different channel plasmon polariton (CPP) waveguides; trenched-groove. V-groove and the suggested three trenched structure over a specific spectral range (200 - 550 THz). The selected frequency band is chosen to ensure the existence of the CPP fundamental mode. The reported design offers a very high FOM at a low frequency band of (200-350 THz) compared to the well-known V-groove structure. However, the lateral mode radius of the suggested three trenched structure is slightly smaller than that of the V-groove structure. For a high frequency band of (350 - 550 THz), the FOM is still higher than that of the V-groove structure while the lateral mode radius r3db is slightly greater than that of the V-groove structure.

Moreover, the modal analysis of a novel design of hybrid long-range plasmonic waveguide is introduced and analysed using the full-vectorial finite difference method as well. The analysed parameters are the real effective index, propagation length, and coupling loss. In addition, the bending analysis of that waveguide has been included.

The coupling has been performed between three different waveguides. A straight dielectric waveguide couples through a straight hybrid long-range plasmon waveguide to a uniformly bent hybrid one. Using the high index materials as a cap for the hybrid waveguides reduce the propagation loss and optimum bending radius as well.

Date of Award	Jun 2013
Original language	English