Self-defocusing/focusing of a relativistic laser pulse in a multiple-ionizing gas
Department of Physics, Indian Institute of Technology, 110016 New Delhi, India
Corresponding author: a email@example.com
Revised: 7 September 2004
Published online: 14 December 2004
A fast rising flattop high power laser pulse, with Gaussian intensity distribution along its wavefront, causes single and double ionizations of the gas through which it propagates. The foot of the pulse causes single ionization of the gas and creates a sharp radial density profile resulting in strong defocusing of the front part of the pulse. After a little while, single state ionization saturates, creating a flat density profile in the axial region and weakening the divergence of the pulse. As the intensity of the pulse rises further, second state ionization occurs, causing strong defocusing of the beam. Later in time when the second state ionization saturates, the relativistic mass nonlinearity together with the electron cavitation tends to focus the pulse.
PACS: 52.38.Hb – Self-focussing, channeling, and filamentation in plasmas / 42.65.Jx – Beam trapping, self-focusing and defocusing; self-phase modulation
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2005