Numerical simulation of the main characteristics of a high-pressure DF–CO2 laser for amplification of picosecond laser pulses

The gain characteristics of the medium of a pulsed DF–CO₂ laser in the ten-micron region at the working gas pressures from 1 to 2.5 atm, which were experimentally determined in [4], are numerically simulated using a scheme that includes the main chemical and relaxation processes. It is shown that the chosen scheme of processes makes it possible (i) to numerically describe the experimental data on the temporal behaviour of gains; (ii) to explain the reason for early degradation of gains (at the degree of D₂ transformation of about 20%); (iii) from comparison of experimental and calculated temporal gain profiles, to determine the degree of photodissociation of F₂ molecules, which is an important parameter determining the operation of pulsed chemical DF – CO₂ lasers; and (iv) to predict the gain characteristics of working mixtures depending on their composition and pressure and on the initiation parameters. The predicted gains in the mixtures of the optimal composition at a pressure of 2.5 atm, a degree of dissociation of F₂ molecules per flash ~1%, and a flash duration at half-width of ~3 ms are ~7 m^-1.