Abstract
In this work, multiple filamentation competition of femtosecond pulse in methanol is studied both experimentally and numerically. The visualization of multiple filamentation competition has been realized in the experiment performing the three-photon fluorescence of Coumarin 440. The random changes of multiple filamentation stemmed from the jitter of the peak laser intensity ratio of initial hot spots are first observed directly and visually, which can be well explained by a simplified (2D+1)-dimensional model.
Highlights
The filamentation is the result of the dynamic counteraction of the optical Kerr effect induced self-focusing and the defocusing effect of the self-generated plasma[1,2,3,4,5]
In order to get coherent multiple filaments during the nonlinear propagation of femtosecond laser pulse, the blade for straight edge diffraction and the two irises for spatial filtering are assembly employed to produce the expected more than one hot spots across the beam profile
The relative intensity distributions of the femtosecond laser filaments are characterized by employing the convenient digital image processing technology
Summary
The filamentation is the result of the dynamic counteraction of the optical Kerr effect induced self-focusing and the defocusing effect of the self-generated plasma[1,2,3,4,5]. The underlying physical mechanism of multiple filamentation is due to the non-uniform wave front[18] by inherent imperfection of the laser or the external perturbation such as turbulence in air[19, 20] or the passage through an optical component, etc. These filaments are not independent as a result of the competition of energy from the whole pulse’s background reservoir into their own self-foci[3, 21]. It is observed that the random changes of multiple filamentation from shot to shot because of the power and corresponding ratio perturbations of input beam, which can be well reproduced by a simplified (2D+1)-dimensional model
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