Self-heterodyne detection of backscattered radiation in single-mode CO2 lasers

Self-heterodyning in dc-discharge-pumped single-mode CO₂ lasers is analysed theoretically and studied experimentally under strong and weak feedback conditions. Relations for the autodyne gain and modulation depth due to the effect of backscattered radiation with a Doppler-shifted frequency are obtained. Nonlinear distortions of the autodyne signal caused by a strong laser — target feedback are studied. It is shown that the autodyne detection of backscattered radiation in CO₂ lasers can be considered linear even in the case of strong laser beam distortions (nonlinear distortions below 5%).