Contrast enhancement and advanced laser pulse diagnosis techniques

This studentship will be hosted within the Plasma Physics group at Imperial College. The majority of the experimental work will take place in the Blackett Laboratory Laser Consortium under the supervision of Prof. Roland A Smith and new instruments developed over the course of the project will be made available for testing on site at AWE. The project will investigate mechanisms for the degradation of temporal contrast on picosecond timescales. Potential candidates include incoherent scattering from diffraction gratings in the pulse stretcher and amplitude noise on the temporal profile of the pump pulse when using parametric amplification processes. This work is also well aligned to other major projects hosted by Imperial, including work funded by DSTL and the US AFOSR to develop new mid-IR high power laser sources, providing a unique environment in which to investigate wavelength scaling of contrast degradation processes.

The project will also address issues associated with Chirped Pulse Amplification using large aperture beams where imperfect wavefront quality and processes such as chromatic aberration can lead to distortion of the temporal intensity profile across the aperture of a pulse compressor. This can be true even where the wavefront of the beam is nominally flat. This problem of wavefront distortion leads to temporal broadening in the far-field (at focus, the point where most physics experiments are conducted) relative to the measured pulse duration. Typically pulse duration measurements are made with a sub-sample of the beam aperture in the near-field. The pulse can be locally short within this sample, but globally longer. For this reason the project will aim to develop instruments that can characterise this at large aperture.