Theory of nonlinear and amplified surface plasmon polaritons

Abstract

This thesis presents a study of Surface Plasmon Polaritons (SPPs) inhybrid metal-dielectric waveguides. The embedding of metal in nanostructuredphotonic components allows for manipulating and guidinglight at the subwavelength scale. Such an extreme confinement enhancesthe nonlinear response of the dielectric medium, which is importantfor applications in optical processing of information, but ispaid in terms of considerable ohmic loss in the metal. It is, however, possible to embed externally pumped active inclusions in the dielectricin order to compensate for the metal loss. A novel perturbativetheory for Maxwell equations is introduced and applied to variousnonlinear metal-dielectric structures, deriving the propagation equationfor the optical field. The nonlinear dispersion law for amplifiedSPPs, filamentation and dissipative plasmon-soliton formation havebeen studied, revealing intrinsic core and tail instabilities that preventsolitons to propagate over long distances. Stable propagation ofplasmon-solitons can be achieved in insulator-metal-insulator structureswith active and passive interfaces. The active SPP is coupledwith the passive SPP, which absorbs the perturbations destabilisingthe zero background of the soliton. Theoretical modelling of opticalpropagation in metal-dielectric stacks predicts a modified two-bandstructure, allowing for gap/discrete plasmon-soliton formation. Lossand nonlinear parameters in subwavelength nanowire waveguides areevaluated and compared to the results obtained by other researchgroups. In all calculations, particular attention is paid in consideringboundary conditions accounting for loss and nonlinear corrections,which contribute to the propagation equation with a surface term thatbecomes significant in the subwavelength regime.

Date of Award	1 Sept 2011
Original language	English
Awarding Institution	University of Bath
Supervisor	Dmitry Skryabin (Supervisor)