Supersonic regimes of plasma expansion during optical breakdown in air

Abstract

Expansion regimes of plasma (fast ionization wave, laser supported radiation wave, and laser supported detonation wave) produced by laser–induced breakdown in air have been studied. To determine a pattern of plasma expansion a numerical investigation of propagation velocity dependence on laser radiation intensity was used. Calculation results agree with the experimental data and show that the most expected high-speed mechanism is fast ionization wave.

Infrared nanosecond laser-metal ablation in atmosphere: Initial plasma during laser pulse and further expansion

“…Mechanisms of supersonic plasma expansion, including fast ionization wave (FIW), laser supported radiation wave (LSRW), and laser supported detonation wave (LSDW) were carefully studied in Ref. 24 …”

High-speed two-frame shadowgraphy for velocity measurements of laser-induced plasma and shock-wave evolution

“…A great interest in instantaneous-velocity measurements of plasma and shock waves produced by highintensity, nanosecond laser pulses arises from many laser-assisted applications, where the shock-wave peak pressure, which is related to the shock-wave propagation speed [10,20], is a crucial parameter. Since these expansion velocities exceed 100 km=s [21,22], successive 2D images of a single event should be captured in a time interval shorter than 1 ns. In addition, to get insight into the development of plasma within the few-nanosecondexcitation-laser pulse, time delays below 1 ns are also mandatory.…”

“…Here we measured the instantaneous axial velocities, v, of the plasma and the shock-wave evolution toward the excitation-laser radiation as a function of the time t after the breakdown initiation. The coordinate of an individual point ðv; tÞ is calculated as Here, a significant measurement noise arises from the different mechanisms of plasma expansion [1,21]. The higher axial velocities (e.g., 300 km=s in Fig.…”

Laser-Induced Discharge Propagation Velocity in Helium and Argon Gases

“…10) Moreover, Raizer's lateral expansion 11) effect on LSD termination has been investigated by Ushio et al 12) The regime transition was also predicted via Hugoniot analysis by Shimamura et al 13) Supersonic expansion regimes of plasma due to laserinduced breakdown have been characterized by u LID as a function of S. These regimes, in an increasing order of dis-charge velocity for a given S, include the LSD wave, 8,11,[14][15][16] laser-supported radiation wave (LSRW) and fast ionization wave (FIW). [17][18][19][20] This study, however, focuses on the LSD wave regime at S < 10 3 GWm ¹2 because FIW and LSRW regimes at S > 10 3 GWm ¹2 do not possess sufficient pressure build-up for an efficient propulsive effect.…”