Theory of shock wave propagation during laser ablation

Abstract

Laser ablation consists of three coupled processes: (i) heat conduction within the solid, (ii) flow through a discontinuity layer (evaporation wave) attached to the solid surface, and (iii) shock wave expansion of the laser induced plume. In this paper, a one-dimensional solution for all three coupled processes is presented. The heat conduction and the evaporation wave are solved numerically. The shock wave expansion of the laser induced plume, however, is solved analytically, to our knowledge, for the first time; analytical solutions for the classic Riemann problem have been employed to solve the transient propagation of the strong shock wave. This model provides a sound theoretical basis for the analysis of the laser ablation process. The temperature, pressure, density, and velocity of the laser induced plume at different laser intensities, back temperatures, back pressures, and ambient gas species are calculated. The effects of the laser intensity, back temperature, back pressure, and ambient gas species are analyzed. The theoretical results provide insight into experimental results available in the literature.

Pulsed laser ablation in liquid for micro-/nanostructure generation

“…The absorption is significant for ns ablation at relatively low irradiances, leading to maximum vaporization and ionization. Even at irradiances of 0.2-1.0 GW/cm 2 near the ablation threshold, a considerable part of the ablation plume could be ionized [59,60], namely, forming plasma. The plasma ionization can be calculated by the Saha equation [61] n m+1 n e n m = 2 u m+1 u m 2 m e k B T h 2…”

Insight into electronic mechanisms of nanosecond-laser ablation of silicon

“…24,25,[44][45][46] This relatively simple model gives a good description of experimental data on the material melting and ablation thresholds and on mass removal without using any adjusting parameters or with a minimum adjustment which, however, can be physically founded. By being incorporated into a number of combined approaches, [47][48][49][50][51][52] it has allowed a proper description of the interrelation between the target state and the laser-induced plume behavior including backward deposition of the ablated products. 50,52 In the model, the absorption of the laser light by the target material is described by the following general Beer-Lambert law, which implies a linear relationship between the absorptance and the concentration of absorbing centers:…”

Comparison of kinetic theory models of laser ablation of carbon

“…8 The choice of ␤ = 1 was made due to oscillation appearing at higher values of ␤. 8 The choice of ␤ = 1 was made due to oscillation appearing at higher values of ␤.…”

“…5,8,18 According to Gusarov et al 5 the plasma effects can be disregarded for nanosecond laser pulses at low fluence not exceeding several joule per centimeter square. We neglect the laser penetration into the solid and do not account for plasma effects, such as ionization and the laser energy absorption in the gas phase ͑the shielding effect͒.…”