Coherent control of long range surface plasmons

• Main Author: Golby, C
• Format: Dissertation
• Language: English
• Published: University of Cambridge 2004

In this dissertation we will investigate the possibility of the Coherent Control of Surface Plasmons. Such Coherent Control will be defined as the ability to excite particular Surface Plasmon spectral components using a femtosecond laser pulse and to control their removal and enhancement using a second pulse, as a function of the temporal separation of this second pulse from the first. A number of different possible device structures, materials and laser sources are investigated theoretically and experimentally. This leads to a demonstration of the removal of Surface Plasmon spectral components of our choice in a Surface Plasmon wave-guide by varying the time separation of exciting double-pulses from an actively stabilised Mach-Zehnder interferometer. We have termed such a mechanism propagating Coherent Control as a result of the travelling wave nature of the Surface Plasmon excitations. This work is supported by theoretical models of decay processes and coupling efficiency which match successfully with experiment. An analysis implying significantly lower dispersion for Surface Plasmons propagating in the structures fabricated than for light travelling in silica is performed. In addition, we investigate in detail the possibility of the static Coherent Control of Surface Plasmons, that is, Coherent Control at the point of excitation. Computer models of device structures, experimental control and measurement of excitation bandwidths and experimental attempts at Coherent Control allow us to place limits on the possibilities of success in this area. We conclude that additional fabrication outside the scope of this project is required for this form of Surface Plasmon Coherent Control; a route is detailed.