Interaction of Light Filaments Generated by Femtosecond Laser Pulses in Air

The interaction of two light filaments propagating in air is simulated. Simulations show that the interaction of the two light filaments displays interesting features such as attraction, fusion, repulsion, and spiral propagation, depending on the relative phase shift and the crossing angle between them. A long and stable channel can be formed by fusing two in-phase light filaments. The channel becomes unstable with the increase of the crossing angle and phase shift. The interaction of two light filaments in different planes is studied and the spiral propagation is observed.

Figure 1

(a) The spatiotemporal intensity distribution formed by an input beam with a 0.2 mJ energy. (b) The energy fluence distribution (${\mathrm{fluence}}_{\mathrm{iso}}=1.65$) of the laser beam with the propagation distance $z$ under the same condition as (a).

Figure 2

(a) The spatiotemporal intensity distribution of two interacting bullets which are in parallel and in-phase. (b), (c), (d), (e), (f) The energy fluence distribution (${\mathrm{fluence}}_{\mathrm{iso}}=1.65$) of two parallel bullets with a separating distance $a=0.5\mathrm{mm}$ and relative phase shift $\varphi =k\pi$, $k=0$ (b); $k=0.25$ (c); $k=0.5$ (d); $k=0.75$ (e); $k=1$ (f).

Figure 3

The energy fluence distribution of two interacting bullets with a separating distance $a=0.5\mathrm{mm}$, individual incident angle $\theta$, and relative phase shift $\varphi$; (a) $\theta =0.01°$ and $\varphi =0$, (b) $\theta =0.1°$ and $\varphi =0$, (c) $\theta =0.01°$ and $\varphi =\pi$, (d) $\theta =0.1°$ and $\varphi =\pi$.

Figure 4

The energy fluence distribution (${\mathrm{fluence}}_{\mathrm{iso}}=2.99$) of two bullets with a separating distance $a=0.5\mathrm{mm}$ in the $x$ direction and $b=0.2\mathrm{mm}$ in the $y$ direction, and incident angle $\theta$ and relative phase shift $\varphi$; (a) $\theta =0.01°$ and $\varphi =0$, (b) $\theta =0.1°$ and $\varphi =0$, (c) $\theta =0.01°$ and $\varphi =\pi$, (d) $\theta =0.1°$ and $\varphi =\pi$.