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Title: Ultrafast light sources and methods for attosecond pump-probe experiments
Author: Fabris, Davide
ISNI:       0000 0004 7233 0017
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2015
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In this thesis I describe the development of novel light sources to be applied in attosecond pump-probe experiments, together with new methods dedicated to their characterisation and optimisation. Femtosecond pulses are a necessary tool to enter the attosecond domain. For this reason their development is a key element to unlock more capabilities in pump-probe attosecond experiments. The dynamics of generation and compression of few-cycle femtosecond pulses has been studied in a hollow core fibre system. The carrier envelope phase stability performance under increasing input power to the fibre system has been examined systematically, showing the effects of ionisation on the carrier envelope phase stability. Two characterisation techniques have been developed to measure ultrafast femtosecond pulses. A version of the d-scan technique has been demonstrated in the single shot regime for the first time, extending the utility of this diagnostic. An all optical technique (ARIES) for the characterisation of the full waveform of a femtosecond pulse has been developed, exploiting the high harmonics generation process and the sensitivity of the cut-off emission to the instantaneous amplitude of the generating electric field. The main results of the thesis are concerned with the generation of isolated attosecond pulses in new spectral regions. Vacuum ultraviolet few-femtosecond and attosecond pulses have been generated by filtering with metallic foils the high harmonics emission driven by sub-4 fs pulses, and were characterised with the attosecond streaking technique. When using indium as spectral filter a pulse duration of 1.7±0.1 fs was measured at a photon energy of 15 eV. When using tin as spectral filter a pulse duration of 585±31 as was measured at a photon energy of 20 eV. The experimental techniques developed in this thesis allow these pulses to be generated simultaneously with a XUV pulse with a measured duration of 270±25 as. This work will open new opportunities for pump-probe experiments, for example studies of ultrafast charge migration in large molecules.
Supervisor: Tisch, John ; Marangos, Jon Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral