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Title: Stopped light in passive and active plasmonic and metamaterial waveguides
Author: Pickering, Timothy William
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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The phenomena of slow and stopped light have attracted a growing interest in recent years, not only in relation to fundamental physics but also due to the possibility to enhance the density of states over a broad bandwidth. In this thesis the effects of both loss and gain on slow and stopped light are investigated in a representative metamaterial and plasmonic waveguide setting, using both semi-analytic calculations and numerical time-domain simulations. Initially the influence of material loss on the ability to stop light in these passive structures is considered. By directly measuring the propagation of wavepackets it is demonstrated that extremely low group velocities, with deceleration factors of the order of 200,000, can be achieved even in the presence of realistic material loss, resolving a previous dispute that this would not be possible. It is further shown that stopped light in the plasmonic waveguide is robust to low levels of surface roughness, currently a limiting factor in other slow light devices such as photonic crystal waveguides. The inclusion of gain materials into the waveguides is then investigated for loss compensation. Here full compensation of losses and even amplification of the modal fields is observed while maintaining zero group velocities. Importantly for the metamaterial waveguide it is found that the effective negative refractive index is maintained even in the amplification regime, as previously it had been suggested this would not be possible. Finally it is shown that in the amplification regime stopped light provides an inherent feedback mechanism leading to the dynamic formation of a lasing mode. The properties of these stopped-light lasing states are studied and it is shown that subwavelength localisation of the modal fields can be achieved, thus presenting a new route to creating nanoscale light sources.
Supervisor: Hess, Ortwin Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available