Filamentation of the focused Ti: Sapphire laser pulse in air at two harmonics
- PDF / 277,415 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 41 Downloads / 114 Views
PHYSICS
Filamentation of the Focused Ti : Sapphire Laser Pulse in Air at Two Harmonics D. V. Apeksimova, O. A. Bukinb, E. E. Bykovaa, Yu. E. Geintsa, S. S. Golikc, A. A. Zemlyanova, A. A. Il’inb, A. M. Kabanova, G. G. Matvienkoa, V. K. Oshlakova, A. V. Petrova, and E. B. Sokolovab a
Zuev Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences, pl. Akademika Zueva 1, Tomsk, 634021 Russia email: [email protected] b Institute of Automation and Control Processes, Far East Branch, Russian Academy of Sciences, ul. Radio 5, Vladivostok, 690041 Russia email: [email protected] c Far East Federal University, ul. Sukhanova 8, Vladivostok, 690950 Russia email: [email protected] Received June 15, 2012
Abstract—The results of experiments on the filamentation dynamics of highpower ultrashort Ti : sapphire laser pulses with wavelengths of 800 and 400 nm upon their sharp focusing in air are presented. The depen dences of the position and dimensions of the plasma channel that forms in the region of the nonlinear beam focus on the laser pulse power are obtained. The spectra of the laser pulse during its filamentation are mea sured. DOI: 10.1134/S1063780X13070106
INTRODUCTION The selffocusing of highpower ultrashort laser radiation pulses belongs to those physical phenomena in which the optical nonlinearity of a medium mani fests itself in the most vivid way. This nonlinearity results in a series of effects such as filamentation of a beam [1, 2], formation of plasma [3], conical emission [4], generation of a supercontinuum [5], and emission of waves in the centimeter range [6]. The current state of this problem is most completely described in reviews [7–9] and studies [10–12]. The physical cause of the selffocusing is the cubic optical polarizability χ(3) of a medium that causes a selfinduced increase in the refractive index in regions with an enhanced radi ation intensity and the subsequent crosssection com pression of the laser beam. In gases, a collapse of the beam is prevented by plasma resulting from the photoionization of the plasma molecules. Inside the laser beam, highly intense dynamic structures (light filaments) form, which are stable against disturbances over a rather extensive path segment. In experiments on the femto second light filamentation, the track of the filaments is recorded, as a rule, in the form of channels luminous in the visible region the luminescence of which is caused by the continuous spectrum, the bands of the molecular nitrogen, and the lines of nitrogen and oxy gen atoms and ions.
A specific feature of the sharply focused ultrashort light filamentation, in contrast to a parallel or colli mated beam, is the fact that the filamentation occurs in a small volume of the focal constriction (focal waist). At the same time, in the nonlinear focus, extreme densities of the light wave power can be achieved [13–15] on the orders close to the intra atomic magnitudes. In this case, the radius of the plasma column can be merely several micrometers and the characteristic length of t
Data Loading...
