Professor Simon Hooker

Abstract:

The resolution obtained with coherent diffractive imaging (CDI) is limited by a number of factors, one of which is the transverse coherence of the illuminating beam. For a successful reconstruction, it is accepted that the illuminating beam should have a lateral coherence length of at least twice the largest linear dimension of the sample

Abstract:

Driving bright high-order harmonic generation (HHG) with few-μJ pulses is a crucial step towards compact, high average power sources of coherent extreme ultraviolet (XUV) radiation for time-integrated applications including imaging. Unfortunately, reaching a sufficiently strong E-field to perform HHG with these pulses requires tight focusing, greatly reducing the interaction volume. An elegant solution to this problem is to restrict HHG to a hollow waveguide [1] and in particular a photonic crystal fiber [2]. Strong reabsorption in the XUV prohibits the use of multi-atmosphere pressures to achieve phase-matching [3], and instead quasi-phase-matching (QPM) is preferred. Here we demonstrate QPM of HHG for the first time within a gas-filled PCF.

Abstract:

We investigate HHG in gas-filled PCFs with microjoule driving lasers. QPM is implemented for the first time, enhancing the flux at 30 eV by a factor of 60.

Abstract:

We demonstrate experimentally the resonant excitation of plasma waves by trains of laser pulses. We also take an important first step to achieving an energy recovery plasma accelerator by showing that a plasma wave can be damped by an out-of-resonance trailing laser pulse. The measured laser wakefields are found to be in excellent agreement with analytical and numerical models of wakefield excitation in the linear regime. Our results indicate a promising direction for achieving highly controlled, GeV-scale laser-plasma accelerators operating at multikilohertz repetition rates.