Scaling of the generation of high-order harmonics in large gas media with focal length
- Service des Photons, Atomes et Molecules, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex (France)
We present theoretical and experimental results on high-order harmonic generation in a low-density few-centimeter-long gas medium (L{sub med}{<=} 10 cm). We study the dependence with focal length of harmonic efficiency. Theoretically, we consider in detail the generation of the 25th harmonic of a short pulse Ti:sapphire laser in argon. Within the strong-field approximation for the atomic dipole, and a complete account of the macroscopic propagation, we compute the number of photons produced as a function of the medium parameters and the focusing conditions. The simulations show that, at constant intensity, the emission of the 25th harmonic scales with the focal length as {approx}f{sup 4} at low pressure (P=2 Torr) and as {approx}f{sup 6} at higher pressure (P=5 Torr). At constant laser energy, we find that the harmonic signal scales approximately as f{sup 2} at low pressure and as f{sup 4} at higher pressure. Those numerical results are compared with experimental data.
- OSTI ID:
- 22095457
- Journal Information:
- Physical Review. A, Vol. 84, Issue 5; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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