Professor Simon Hooker

Abstract:

We investigate quasi-phase-matching of high harmonic generation over a range of harmonic orders using trains of up to 8 uniformly-spaced counter-propagating pulses, produced using an array of birefringent crystals. © 2012 OSA.

Abstract:

We investigate quasi-phase-matching of high harmonic generation over a range of harmonic orders using trains of up to 8 uniformly-spaced counter-propagating pulses, produced using an array of birefringent crystals. © 2012 OSA.

Abstract:

Temporally resolved, spatially integrated measurements of the temperature of the plasma channel formed by a hydrogen-filled discharge capillary waveguide are presented. Plasma temperatures of 4-7 eV are measured for peak discharge currents between 80 and 150 A. It is demonstrated that laser-triggering the capillary discharge enables capillary discharges with a peak current as low as 23 A to be driven, reducing the plasma temperature to approximately 3 eV. This plasma temperature meets the requirements of a recently proposed soft x-ray recombination laser. © 2011 IOP Publishing Ltd.

Abstract:

The longitudinal coherence of free-electron laser (FEL) radiation can be enhanced by seeding the FEL with high harmonics of an optical laser pulse. The radiation produced by high-harmonic generation (HHG), however, has a fast-varying temporal profile that can violate the slowly varying envelope approximation and limited frequency window that is employed in conventional free-electron laser simulation codes. Here we investigate the implications of violating this approximation on the accuracy of simulations. On the basis of both analytical considerations and 1D numerical studies, it is concluded that, for most realistic scenarios, conventional FEL codes are capable of accurately simulating the FEL process even when the seed radiation violates the slowly varying envelope approximation. We additionally discuss the significance of filtering the harmonic content of broadband HHG seeds. © 2011 American Physical Society.