An efficient control of ultrashort laser filament location in air for the purpose of remote sensing

• Published in: Applied physics. B, Lasers and optics Lasers and optics, 2006-10, Vol.85 (1), p.55-58
• Main Authors: LIU, W, THEBERGE, F, DAIGLE, J.-F, SIMARD, P. T, SARIFI, S. M, KAMALI, Y, XU, H. L, CHIN, S. L
• Format: Article
• Language: English
• Subjects: Astronomy; Beam trapping, self-focusing and defocusing; self-phase modulation; Beams (radiation); Chirp; Earth, ocean, space; Exact sciences and technology; Expansion; Filaments; Fundamental areas of phenomenology (including applications); Fundamental astronomy and astrophysics. Instrumentation, techniques, and astronomical observations; Historical astronomy and archaeoastronomy; and other topics in fundamental astronomy and astrophysics; instrumentation, techniques, and astronomical observations; Hot spots; Lasers; Nonlinear optics; Optics; Physics; Telescopes; White light
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-006-2337-4

The unavoidable hot spots in a practical terawatt level laser pulse will self-focus in air at a short distance. The short distance cannot be changed significantly by only controlling the chirp or divergence. We overcome such early self-focusing by using a telescope, which enlarges the diameter of the beam, thus that of the hot spots. The telescope's effective focal length is much shorter than the self-focusing distance of both the enlarged beam and the hot spots. Then, the resulting filaments merge into the geometrical focus whose position is controllable by the telescope. This technique also minimizes the generation of white light.