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Title: Development of extreme ultraviolet harmonic sources from intense laser interactions
Author: Yeung, Mark Kai Ho
ISNI:       0000 0004 2745 5427
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2012
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Laser based sources of high order harmonic radiation have been the subject of great interest over the last three decades due to the promise they hold of providing widespread laboratory access to coherent extreme ultraviolet and X- ray light. The short wavelength nature of this harmonic radiation, combined with its ability to support pulses with durations on the scale of attoseconds, permits the study of microscopic processes on unprecedented timescales. This thesis reports on a body of experimental and theoretical work aimed at further developing these unique sources. High intensity laser interactions with gaseous media is one such process that leads to the generation of high order harmonic radiation. However, this scheme is limited to low generation efficiencies due to poor phase matching of the harmonic waves which limits the length over which the harmonic field can build up. Interspersing the interaction length with a low ionisation potential gas is shown to successfully achieve quasi phase matching in an easily extendible setup that, in principle, could lead to very high generation efficiencies. High frequency radiation can also be generated from solid density plasma surfaces driven at relativistic velocities by an ultra intense laser. To date, most of the results in this field have been for the reflected direction, however high harmonic orders have also been observed in transmission for very thin foils. Presented here are recent results showing that the transmitted spectrum contains harmonics extending to very high orders. Additionally it is shown that they are spatially coherent and that the generation process can be controlled through the ellipticity of the driving laser. Finally, numerical simulations of surface harmonic generation from a blazed grating show that the generated spectra are angularly dispersed. Under the right conditions, significant diffraction efficiency into a single diffraction order for a particular harmonic can be achieved yielding a near monochromatic beam of short wavelength radiation
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available