Visualization of focusing-refocusing cycles during filamentation in BaF2
Abstract
Filamentation occurs within a 1.5 cm-long crystal of BaF2 during the propagation of intense, ultrashort (40 fs) pulses of 800 nm light; a systematic study as a function of incident power enables us to extract quantitative information on laser intensity within the condensed medium, the electron density and the six-photon absorption cross section. At low incident power, a single filament is formed within the crystal; two or more filaments are observed along the direction transverse to laser propagation at higher incident powers. Further, due to fluorescence from six-photon absorption (6PA), we are able to map the intensity variation in the focusing-refocusing cycles along the direction of laser propagation. At still higher incident powers, we observe splitting of multiple filaments. By measuring the radius ( L min ) of single filament inside BaF2, we obtain estimates of peak intensities ( I max ) and electron densities ( ρ max ) to be 3.26×1013 W cm-2 and 2.81×1019 cm-3, respectively. Use of these values enables us to deduce that the 6PA cross-section in BaF2 is 0.33×10-70 cm12 W-6 s-1.
- Publication:
-
Applied Physics B: Lasers and Optics
- Pub Date:
- February 2009
- DOI:
- 10.1007/s00340-008-3317-7
- Bibcode:
- 2009ApPhB..94..259D
- Keywords:
-
- 52.38.Hb;
- 42.65.Jx;
- 42.65.Tg;
- 33.80.Wz;
- 52.35.Mw;
- 52.38.Hb;
- 42.65.Jx;
- 42.65.Tg;
- 33.80.Wz;
- 52.35.Mw;
- Self-focussing channeling and filamentation in plasmas;
- Beam trapping self-focusing and defocusing;
- self-phase modulation;
- Optical solitons;
- nonlinear guided waves;
- Other multiphoton processes;
- Nonlinear phenomena: waves wave propagation and other interactions