The Blackett Laboratory Laser Consortium

Introduction

The Laser Consortium was founded just over a decade ago to bring together expertise in high intensity short-pulse lasers and intense laser-field-matter interactions. A broad range of experimental and theoretical investigations are underway at Imperial College and Oxford University (where that part of the programme is directed by Professor Keith Burnett).

Laser Consortium experimental programme

In the last decade there has been a revolution in laser science driven by developments in short pulse laser technology that now enable table top lasers to produce optical powers well in excess of a terawatt and pulses as short as 10 fs. In many systems, where the timescales of intrinsic importance are very fast i.e. from 1ps () to 1fs (), the availability of these intense short pulses has had a profound impact. The Blackett Laboratory Laser Consortium is a programme of experimental and theoretical research that is exploring this new frontier of science. We are making pioneering contributions to this research through our work on nonlinear optics, plasma physics, and molecular dynamics. Recently (April 2000) we were awarded a £1.4M programme grant by EPSRC to expand our work in this area.

Our main tools are two state-of-the-art CPA laser systems. One of these, a glass based system, can deliver 1J in 2ps. It will shortly be up-graded to deliver 1J in a sub-500fs pulse. The other laser is based upon Ti:Sapphire amplifiers and can deliver similar powers but in a pulse duration of only 60fs. These laser systems can produce peak intensities in excess of . These extreme power densities and electric fields can radically alter the nature of matter. The interplay of matter and energy under these circumstances produces some truly spectacular effects, for example the simultaneous absorption of ~100 visible photons by a single atom and subsequent emission of the total energy as a single X-ray photon. This process (high harmonic generation) has been harnessed to produce a truly unique source of ultra-short (< 10 fs) pulses of coherent, directional soft X-rays. The energy that is available from the laser field can also be coupled to particles. In atomic clusters, for example, 1000 atom aggregates can be rapidly heated by the laser and its subsequent explosion accelerates ions to MeV energies. The energetic particles produced in cluster explosions have recently been used to carry out table-top thermonuclear fusion and generate ultra short (~100 ps) bursts of neutrons. At intensities in the range ultra-short optical pulses can be used to control the dynamics of molecular reactions. This is achieved through the creation of nuclear wavepackets and the simultaneous modification of the molecular energy level surfaces through which these wavepackets can move.

The main issues to be addressed by the current programme are summarised in figure 1. The programme includes ongoing laser system developments (e.g. sub-10fs pulse generation and amplitude/phase pulse tailoring) as well as new investigations into ultra-fast processes at high intensity.

We have active collaboration with many other leading research groups around the world including; Rochester University, LLNL, Weizmann Institute, Kaiserslautern, Wuerzburg and Lund. In addition to funding from the EPSRC we also have EU support under the COCOMO IHP programme. Currently there are 8 project students, 5 PG students, 3 PDRA's, 2 full time technicians and a Marie-Curie Senior Fellow engaged in these experiments.

Funding:

This work is funded by: a UK Engineering and Physical Sciences Research Council Programme Grant with the MOD (GR/N11292); the British council; the EU, Marie Curie (HPRN-CT-1999-00346) and COCOMO (HPRN-CT-1999-00129).