Parametric study of degenerate four-wave mixing and phase conjugation of CO2 and CO lasers radiation in their inverted medium

Summary form only given, as follows. Parametric study of degenerate four-wave mixing and phase-conjugation (PC) of e-beam controlled discharge pulsed CO₂ and CO laser radiation in their inverted media has been carried out experimentally. The influence of the following parameters on energetic and temporal characteristics of PC signal and reflectivity has been studied: input energy (50-300 J/l.Amagat), small signal gain (0.5-2.0 2.0 m^-1) laser mixture contents (CO₂:N₂:He=1:2:7 with high He contents, 1:5:3 with high nitrogen contents; CO:N₂:He=1:4:5), gas pressure (density) (0.1-0.56 atm for CO₂, 0.3 Amagat for CO), reflectivity of output mirror (7.5-65%), single line and multiline laser spectrum (10.6 μm P(20); 9.6 μm P(22), P(24) for CO₂ ; 5.3-5.6 μm and 5.39 μm P_10.9(14) for CO), probe and pumping waves intensity (intensity ratio is 0.02-5.0), geometry (the angle between the probe and pumping wave is 10-40 mrad), coherent parameters (optical delay and polarisation). The maximum PC reflectivity does not exceed 2% for CO₂ and 0.2% for CO lasers. The complicated time-history of the PC signal for pulsed CO₂ and CO lasers reflects the main relaxation processes taking place in the inverted medium and demonstrates the relative role of the two main mechanisms-saturated gain (amplitude) and thermal (phase) ones-which are responsible for formation of transient diffraction gratings in the active medium of CO₂ and CO lasers. The influence of the Q-factor and the intensity ratio of probe and pumping waves on optical quality of the PC signal has been also investigated