High order harmonic generation optimization with an apertured laser beam
Laboratoire d'Optique Appliquée, ENSTA-École Polytechnique (UMR 7639 du CNRS) , 91761 Palaiseau Cedex, France
Corresponding author: a firstname.lastname@example.org
Published online: 24 September 2002
We report a systematic study of high order harmonic generation with an infrared laser apertured by an iris, as a function of the aperture size. Measurements were made of harmonic generation efficiency for different gas species, laser energies and focal geometries. Harmonic efficiencies as a function of aperture show a characteristic peaked shape, which is independent of gas species and harmonic order. A one dimensional, time dependent simulation of harmonic generation in a gas cell, taking into account experimentally measured transverse coherence of the laser, closely reproduces the observed behaviours. We show that the aperture diameter which maximizes harmonic yield is the result of a compromise between considerations of focal geometry and ionization (which favour small apertures); and harmonic dipole amplitude and phase (which favour large apertures).
PACS: 32.80.Rm – Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states) / 42.65.Ky – Harmonic generation, frequency conversion
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2002