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Title: Non-linear optical characterisation of single-walled carbon nanotubes
Author: Sutton, Richard
ISNI:       0000 0001 3492 3696
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2008
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This thesis reports the measurement of non-linear optical properties of single-walled carbon nanotubes (SWNTs). We report results of ‘Z-scan’, pump-probe and spectrally-resolved pump-probe experiments, each of which reveals different aspects of the interesting non-linear optical behaviour of this novel material. Prior to the experimental chapters, we introduce several areas of background material useful in the understanding of our data. We firstly discuss the optical properties of materials, and how they are strongly affected by dimensionality. A brief overview of SWNTs and the source of their interesting optical properties follows. We also address diffusion-limited two-body processes in one dimension, as these are crucial to the interpretation of the presented pump-probe results. The non-linear optical techniques mentioned above are then introduced along with the amplified ultrafast laser system which is the tool for the measurements. The Z-scan technique reveals the magnitude of both absorptive and refractive non-linearities of materials. For our SWNT suspensions we find that the optical Kerr effect, which has many potential applications, is found to be dominated by a thermal lensing effect. Pump-probe measurements of SWNT suspensions are found to reveal very interesting photoexcitation decay characteristics, which we explain using a novel reaction-diffusion picture in which strongly bound excitons diffuse along the SWNT axis before annihilating with a finite reaction rate upon coming into contact with one another. This complex dynamical behaviour, which has not previously been seen experimentally, allows the extraction of fundamentally important parameters such as the diffusion constant and reaction time of the photo-excited excitons. The extension of the pump-probe experiment to incorporate spectral resolution shows that this behaviour is independent of the diameter and chirality of the photoexcited SWNT.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available