Investigation of Gas-Dynamic Processes in Optical Discharges with an Ablating Polymer Wall in Air and Vacuum Conditions

Experimental research results are presented on the formation dynamics and macrostructure of optical discharges of condensed matter of a polymer series (($\mathrm{C}_2$$\mathrm{F}_4)_n$, ($\mathrm{CH}_2$$\mathrm{O})_n$) under the action of a femtosecond laser ($\tau_{0.5} \sim 45–70$~fs) pulses ($I_0 \sim 1013$--$1015$~W/cm$^2$) in the UV--NIR spectral region ($\lambda \sim 266, 400, 800$ nm) under air and vacuum conditions. Electron density distributions in the near-surface area of the optical discharge, vapor expansion, and velocities of shock-wave front propagation are determined for the first time by precise laser pulse micro-interferometry with high spatial and time resolution. The correspondence is shown of the values of the laser ablation spectral-energy threshold, as determined by interference microscopy and the interferometry of a gas-plasma flow. An estimation technique for the total momentum of light-erosion gas–plasma flow in the sub-nanonewton range is proposed and implemented for the first time. The results of comparative analysis are presented on the laser radiation conversion efficiency at different stages of femtosecond optical discharges.