Abstract:
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.