Simulation of free-space optical guiding structure based on colliding gas flows

Preformed plasma channels with parabolic radial density profiles enable the extended and stable optical guiding of high-intensity laser pulses. High-voltage discharge capillaries, commonly used for channel formation, have limited guiding length and opaque walls, complicating the diagnosis of the plasma within. This paper proposes a free-space gas channel produced by the collision of several gas flows. The collision of the gas flows forms an on-axis density depression surrounded by higher density walls. By offsetting the flows, we demonstrated the creation of what we believe is a novel vortex structure that exhibits a long-lived parabolic density profile. Once ionized, the resulting plasma density profile has a near-parabolic dependence appropriate for guiding. We then performed detailed two-dimensional (2D) fluid dynamics simulations to examine the properties and stability of the guiding structure.