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Spatiotemporal moving focus of long femtosecond-laser filaments in air

Ting-Ting Xi, Xin Lu, and Jie Zhang
Phys. Rev. E 78, 055401(R) – Published 14 November 2008

Abstract

The characteristics of filaments formed by femtosecond-laser pulses freely propagating in air are different from those of filaments generated with a focal lens. A scheme combining (2D+1) modeling of the nonlinear Schrödinger equation and ray-tracing method is proposed to provide a fast estimate of the long-range filamentation process in a single-filament regime. A filament with a length of more than 100m is formed by a 10mJ, negative chirped 350fs laser pulse freely propagating in air. A ray-tracing calculation based on the refractive index field obtained from the nonlinear Schrödinger simulation shows that, in the 100m propagation range, the main mechanism of filamentation is the spatiotemporal moving focus induced by the initial distribution of the laser intensity. The analysis of ray trajectories suggests that the energy exchange between background and filament core due to refocusing of light rays can be induced by Kerr self-focusing without the help of the ionization effect. The plasma defocusing can be observed only at a very short distance on the propagation track, and it prevents the collapse of the laser field.

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  • Received 11 June 2007

DOI:https://doi.org/10.1103/PhysRevE.78.055401

©2008 American Physical Society

Authors & Affiliations

Ting-Ting Xi1,2, Xin Lu1, and Jie Zhang1,3,*

  • 1Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
  • 2Department of Physics, Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • 3Department of Physics, Shanghai Jiao Tong University, Shanghai 200240, China

  • *Author to whom correspondence should be addressed. Fax: +86-10-82649356. jzhang@aphy.iphy.ac.cn

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Issue

Vol. 78, Iss. 5 — November 2008

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