We investigate the propagation in air of laser pulses in linear and nonlinear regime. The mathematical model presented in the paper describes the propagation of pulses with narrow-band spectrum, as well as the evolution of broad-band ones. It is shown that the diffraction of pulses with super-broad spectrum or pulses with a few cycles under the envelope is closer to wave type. For such pulses, a new physical mechanism of balance between non-paraxial diffraction and third order nonlinearity appears. We investigate in more detail the nonlinear third order polarization, taking into account the carrier to envelope phase. This additional phase transforms the third harmonic term to GHz terms, which start to generate radiation when the pulse duration reaches the femtosecond range.

Date Published: 15 March 2013
PDF: 10 pages
Proc. SPIE 8770, 17th International School on Quantum Electronics: Laser Physics and Applications, 87701G (15 March 2013); doi: 10.1117/12.2013663

Published in SPIE Proceedings Vol. 8770:
17th International School on Quantum Electronics: Laser Physics and Applications
Tanja N. Dreischuh; Albena T. Daskalova, Editor(s)