Surface plasmon polaritons offer unique opportunities to guide and confine electromagnetic energy over spatial dimensions below the diffraction limit of light, and the recent sophistication of computational, fabrication and characterisation techniques has seen a number of important advances towards the goal of creating optical functionality on a length scale comparable to that of electronic devices. However, because of the inherent loss mechanisms of the metallic material system, there exists a general trade-off between localization and loss in plasmonic devices, and a good understanding and control over this important parameter is required in order to design structures with a desired functionality.

In my talk, I will elucidate this trade-off via recently demonstrated examples of plasmon waveguides based on metallic nanoparticles. Specifically, the design of a hybrid SOI/metal nanoparticle waveguide that shows low losses and can be efficiently excited in the telecommunication window via the use of tapered optical fibres will be presented, with power transfer efficiencies > 75% experimentally demonstrated. Additionally, a critical theoretical comparison between plasmonic cavities and their dielectric counterparts will be presented, focusing on a common description in terms of quality factor and effective mode volume. Such a description can aid the use of plasmonic cavities for applications in cavity quantum electrodynamics and sensing. As an example, I will present a plasmon cavity model of surface enhanced Raman scattering.