Control of multiple filamentation in air

Abstract

In this Letter we provide what is believed to be the first experimental evidence of suppression of the number of filaments for high-intensity laser pulses propagating in air by beam astigmatism. We also show that the number, pattern, and spatial stability of the filaments can be controlled by varying the angle that a focusing lens makes with the axial direction of propagation. This new methodology can be useful for applications involving atmospheric propagation, such as remote sensing.

Femtosecond Filamentation in Air

“…They showed that deterministic vectorial effects could prevail over the amplification of noise in the process of multiple filamentation. A small ellipticity of the input beam should also lead to well determined multiple filamentation patterns [24,25]. Building on this idea, it was shown that multiple filaments can be organized by various control mechanism acting either on the intensity or on the phase of the input field [53,73].…”

Self-compression of 120 fs pulses in a white-light filament

“…As our laser system delivers relatively long >100 fs output pulses, we can replace the focusing mirror by a simple lens, avoiding potential issues with astigmatism, which allows for some simplification. This measure may also to some extent delay spatial break-up of the filament [21]. For the measurements reported in this paper, a lens with a focal length of f = 75 cm is used at a distance of 25 cm to the Brewsteroriented input window.…”

Formation of periodic multifilamentary structures by use of highly elliptic light beams

“…Beam breakup starts evolving along the major axis and ends up with stable and entirely predictable MF patterns. To this regard, reproducible MF patterns by slightly elliptical beams had been observed in various nonlinear media: water [9], air [10], BK7 glass [11], fused silica [12], and carbon disulfide [13], all revealing the universality of the deterministic breakup process.…”

“…The abovementioned modifications to the input beam lead not only to the formation of controllable MF patterns with predictable number of filaments in a desired way, but also significantly improve the beam pointing stability [4,10]. Most importantly, mutual coherence between filaments created by the same laser pulse was first suggested by [14] and later verified by means of interferometric measurements [15].…”