Dual-scale turbulence in filamenting laser beams at high average power

We investigate the self-induced turbulence of high-repetition-rate laser filaments over a wide range of average powers (1 mW to 100 W) and its sensitivity to external atmospheric turbulence. Although both externally imposed and self-generated types of turbulence can have comparable magnitudes, they act on different temporal and spatial scales. While the former drives the shot-to-shot motion at the millisecond time scale, the latter acts on the 0.5-s scale. As a consequence, their effects are decoupled, preventing beam stabilization by the thermally induced low-density channel produced by the laser filaments.

Figure 1

Experimental setup. Values correspond to the high-power beam.

Figure 2

Wandering of the single filament and of the whole moderate-power beam propagating through a turbulent region.

Figure 3

Wandering of the high-power laser beam propagating through a turbulent region.

Figure 4

Trajectory of the moderate-power beam pointing at a repetition rate of 1 kHz, (a) without and (b) with externally imposed turbulence. See also the Supplementary Material [34], Movies 1 and 2, corresponding, respectively, to (a) and (b).

Figure 5

Instantaneous wandering speed $v_{\mathrm{w}}$ of the laser beam.