Transcript High-harmonic generation from noble gases exposed to

High-harmonic generation from
noble gases exposed to intense
laser fields
Gavin Waters
Supervisor: Dr. L. J. Frasinski
Schematic Diagram of Equipment
Diagram: Y. Mairesse et al; 'Attosecond
Synchronization of High-Harmonic Soft Xrays' Science, Vol 302, 28 November 2003,
1540-1543
Three-step Model of HHG
Step 1: Tunnel ionization
Step 2: Quasi-classical electron
acceleration in strong laser field
Step 3: Electron-nucleus
recombination, emission of High
Harmonic photon
Due to this process occurring every
half of the optical cycle of the
driving beam, only photons of
frequency that are odd harmonics
of the driving beam are produced
Diagram: P. Agostini, L. F. DiMauro; 'The
Physics of Attosecond Light Pulses' Rep.
Prog. Phys. 67 (2004) 813-855
Electron Wave-packet Model of HHG
Electron now represented by its
wave-function, ψ
Part of the wave-function, ψg,
remains in the ground state
Remaining part of wave-function, ψc,
interferes with ψg on re-collision
This interference effect leads to an
electron charge oscillation, and the
emission of High Harmonic radiation
Diagram: J. Itatani et al; ' Tomographic
Imaging of Molecular Orbitals' Nature, Vol
432, 16 December 2004, 867-871
Technical Drawing of Apparatus
Side view of the
HHG equipment.
Equipment
designed by J.
Tisch (Imperial
College). The two
main components
shown are HHG
chamber (right)
and mirror
chamber (left).
Diagram: J. Tisch, Imperial College
Technical Drawing of Apparatus
Top down view
of the HHG
equipment.
Red line
represents
driving laser
beam (pulse
duration about
30fs).
Green line
represents HHG
laser beam
(pulse duration
less than 1fs).
Diagram: J. Tisch, Imperial College
HHG equipment used in Saclay
experiment
Mirror Chamber used in Saclay
Experiment
ULL, University of Reading