Interaction of two counterpropagating laser induced plasmas and shock waves in air

Abstract

The interaction of two counterpropagating plasmas and shockwaves due to a 7 ns laser induced breakdown (LIB) of ambient atmospheric air was studied using the 2D emission and shadowgraphic imaging technique. The effect of separation distance (d) between the two plasma sources and their energy ratio on plasma and shockwave evolution is presented. These low density and low temperature plasma sources form a stagnation layer in the interaction zone that showed an interesting dependence on the input energy of the sources. The interaction dynamics of the two counterpropagating plasma plumes and the shock waves in ambient air are compared with that of the respective single plasma source to explicitly bring out the energy exchange during the interaction. The evolution of a plasma jetlet, studied by 2D emission images and shadowgraphic imaging, has shown very good correlation giving valuable insight into the role of a plasma induced shockwave on the expanding plasma. The propagation of the shock front of the high energy source through the plasma of a low energy source is observed to predominantly lead to the formation of a jetlet and its evolution.

Backward Flux Re-Deposition Patterns during Multi-Spot Laser Ablation of Stainless Steel with Picosecond and Femtosecond Pulses in Air

“…on pulse energy and plasma seed separations [70]. One might ask if oxidation during ultrafast laser ablation is significant here, but we have also observed the Jets in pure Nitrogen at 1 atm (10 ps, not reported here) with the aid of a gas cell.…”

“…Two colliding air breakdown plasmas created with high energy, nanosecond laser pulses demonstrated reflection and transmission of expanding shock waves depending on pulse energy and plasma seed separations [ 70 ]. One might ask if oxidation during ultrafast laser ablation is significant here, but we have also observed the Jets in pure Nitrogen at 1 atm (10 ps, not reported here) with the aid of a gas cell.…”

Dynamics of spatially confined ns laser induced atmospheric air plasma and shock waves: visualization vis-à-vis validation

“…Defocused shadowgraphy and self-emission imaging is used for experimentally diagnosing the shock wave evolution, visualizing the gradients of plasma density variation [41][42][43].…”

Effect of focusing plane on laser blow-off shock waves from confined aluminum and copper foils

“…If the magnitude of the stress wave exceeds the shear strength of the material then the un-vaporized part ahead of the affected region ruptures, which eventually leads to the ejection of the blow-off plasma and/or material that evolve with higher velocity in the laser propagation direction [15,16]. It was well established both theoretically and experimentally that the ablated and blow-off plasma formed at the front and rear sides of the target depends on various parameters such as, input laser intensity (energy) [17][18][19][20][21][22], wavelength [23], pulse duration [18,24,25], beam size on the target, thickness of the target material and its properties, surrounding ambient gas pressure conditions [15,16,[26][27][28][29][30] and the effective impedance of the foil and confined materials used [14,31].…”