Overview
My work is in the area of laser - matter interactions with an emphasis on revealing the fundamental principles underlying new classes of laser matter interaction. So for instance the advent of high intensity ultra-fast laser pulses has led to new types of laser interaction with molecules and small clusters which we have been in the forefront of exploring. Similarly the opportunities afforded in ultrafast measurement of matter by X-ray Free Electron Lasers is an important topic of my present research.
This work can be largely categorised into 4 general themes:
1. Coherent VUV/XUV Sources and Applications to Muon Science and Metrology
The most significant work in this category was the development in 1990 of a high efficiency, broadly tunable (120-180nm), resonantly enhanced frequency mixing source of coherent radiation in the VUV. This was widely applied by my group and by others for VUV spectroscopy. The high brightness of the VUV radiation from this source enabled new types of experiment; two of these pioneering applications (in USA and Japan) were worked on by me in the course of the next few years. At the University of Tokyo Meson Science Laboratory (KEK, Tsukuba) the high brightness radiation was used to resonantly ionize slow muonium atoms that were produced in a metal target by an accelerated proton beam. The muons that were liberated by this ionisation were at low temperature and this is a promising source of slow muons (for use e.g. in surface SR studies). At NIST (Gaithersburg) a similar source was used to perform Doppler free two-(VUV) photon spectroscopy to measure the He 1s2 state energy - the value of which is sensitive to two-electron QED corrections.
2. Coherent Control of Chemical and Non-Linear Optical Processes
Most notable in this category was the exploration of the enhancement of non-linear optical processes in coherently prepared atoms. The work has influenced the development of experiments in this area and identified the correct choice of parameters to optimise the conversion efficiency as well as quantified the limits set by for example electron dephasing of the coherence. Further work was instigated by me at the University of Kaiserslautern by transfer of equipment and assisting this group develop their interests in non-linear optical applications of atomic coherence.
3. Intense Laser Interactions with Dense Gases and Clusters
I initiated the Imperial College research programme in the area of laser cluster interactions. Following funding of a proposal I authored we were able to begin our research in this area - fortuitously we were able at this point to hire Todd Ditmire as a post-doc. The publication in 1997 and 1998 of measurements of the ion kinetic energies and charge states from a laser cluster interaction had a large impact on the field of high intensity laser plasma interaction. We have subsequently conducted a number of scaling studies that have further elucidated the mechanisms of laser heating of clusters.
4. Molecules in Strong Fields and Attosecond Science
A major contribution in this area was the earliest identification that the HHG emission from molecules can be related to their structure. This was followed from an earlier series of experiments beginning in 1995. It was only when shorter intense laser pulses became available that I was able to develop these ideas further. Early experiments (2000-2001) pioneered the idea of using aligned molecules. These stimulated theoretical investigations with my postdocs Lappas and Lein that led to the identification of strong electronic interference effects in the recollison process with molecules in 2002. These have recently been seen in experiments by ourselves and others. This work should lead to new ways for studying structural changes in molecules with ultra-fast temporal resolution.
In 2003 I started the UK Attosecond Science project (which I currently coordinate) which has now secured substantial funding and assembled a capability to play a significant role in this emerging field. This proved a highly effective collaboration centred in my group at Imperial that has in the short time since formation risen to become one of the major laboratories in the world in this area of science. It has led on to a major EPSRC Programme Grant "Attosecond Electron Dynamics in Molecular and Condensed Phase Matter" (2011-2017) of which I am Principal Investigator in a collaborative programme of experimental and theoretical research that spans both Physics and Chemistry. A further major funding to investigate "Attosecond Science by the Transmission and Emission of X-rays" (ASTEX) was awarded to me by the ERC (in there Advanced Grant Scheme) in 2012.
Current ERC Support
ASTEX "Attosecond Science by the Transmission and Emission of X-rays" ERC Advanced Grant (2012-2017) (P) (~£2M)
Current EPSRC Support
(P)=Principal Investigator, (C)=Co-Investigator, (R)=Recognised Researcher:
EP/I032517/1 Attosecond Electron Dynamics in Molecular and Condensed Phase Matter" (P) £6.5M
Previous EPSRC Support
(P)=Principal Investigator, (C)=Co-Investigator, (R)=Recognised Researcher:
EP/E028063/1 Control of Electrons by Few-Cycle Intense Laser Pulses (P) £2.5M
EP/C530764/1 Dynamic Imaging Of Matter At The Attosecond and Angstrom Scales (P) £514K
GR/S22400/01 Basic Technologies: Attosecond Technology - Light Sources, Metrology and Applications (C) £1M
GR/R96316/02 The UK Cold Atoms Network: UKCAN (C)
GR/R96316/01 The UK Cold Atoms Network: UKCAN (C)
GR/R82203/01 Modulation of Femtosecond Laser Pulses by Molecular Coherence (P)
GR/N11292/01 THE INTERACTION OF ATOMS, MOLECULES AND CLUSTERS WITH TAILORED HIGH INTENSITY LIGHT PULSES (C)
GR/M15743/01 GIANT KERR NON-LINEARITIES AND SINGLE PHOTON CAVITY CONTROL IN LASER COOLED RUBIDIUM (P)
GR/L58408/01 TEMPORAL EVOLUTION OF POPULATIONS AND ATOMIC COHERENCES EXCITED BY PULSED LASERS (P)
GR/L34334/01 INTERACTION OF INTENSE LASER RADIATION WITH MATTER (C)
GR/L19768/01 ELECTROMAGNETICALLY INDUCED TRANSPARENCY IN NON- LINEAR OPTICS (P)
GR/K47320/01 INTERACTION OF HIGH INTENSITY LASER RADIATION WITH MATTER (C)
GR/J83673/01 ELECTROMAGNETICALLY INDUCED TRANSPARENCY IN NON-LINEAR OPTICS (P)
GR/J02292/01 INTERACTION OF INTENSE LASER RADIATION WITH MATTER. (C)
Collaborators
Prof Majed Chergui, EPFL, Lausanne, Ultrafast dynamics of hydrogen bonding and solvated electrons in water, 2013
Dr Ryan Coffee, Stanford Linear Accelerator Laboratory, LCLS, Ultrafast few-femtosceond pump - probe measurements with X-ray FELs, 2011
Andrius Baltuska, Technical University of Vienna, Multicolour strong field synthesis for optimised HHG, 2011
Professor Phil Bucksbaum, Stanford University, Molecules in strong X-ray fields, 2009
Professor Jonathan Tennyson, University College London, Molecules in strong fields
Prof Paul Corkum FRS, National Research Council, Ottawa, Ultrafast Molecular Imaging
Professor Helen Fielding, University College London, Ultrafast molecular science
Prof Mauro Nisoli, Politechnico di Milano, Attosecond Physics
Prof Ian Walmsley, University of Oxford, Ultrafast Optics
Guest Lectures
Controlling Recollisions for attosecond Measurements, ETH, ETH, Zurich, Zurich, Switzerland, 2012
Attosecond Science at the Blackett Laboratory, Daresbury, STFC, Daresbury, Daresbury, Cheshire, 2012
Attosecond Molecular Science, University of Beijing, Department of Physics, Beijing, 2012
Experimental approaches to HHG Spectroscopy, CORINF Summer School, MPIKS, Dresden, Dresden, Germany, 2012
Attosecond Measurement, EPFL, EPFL, Lausanne, Lausanne, Switzerland, 2012
Ultrafast and Attosecond Science, SUSSP 66, Scottish University Summer School, Heriot Watt, 2010
Ultrafast and Attosecond Science, Rank Meeting, Rank Prize Meeting, Ambleside, UK, 2009
Research Staff
Austin,D
Cooper,B
Diveki,Z
Hoffmann,D
Siegel,T
Susikyan,S
Witting,T
Zair,A
Research Student Supervision
Fabrise,D, Generation of sub-femtosecond VUV pulses
Hung,J, Modelling of attosecond transient absorption
Hutchinson,S, X-ray induced HHG
Hutchison,C, HHG from ablation plumes
McGrath,F, HHG in Organic Molecules
Simpson,E, HHG from Molecules at Surfaces