Self-mixing detection of backscattered radiation in single-mode pulse-periodic CO2 lasers

The self-mixing (autodyne) effect in single-mode CO2 lasers with pulse-periodic (PP) pumping of the active medium is theoretically analyzed and experimentally investigated. A semiempirical model of the autodyne effect in CO2 lasers of this type is developed that allows the laser beat signal to be described from the known shape of the generated pulses. The self-mixing effect in PP CO2 lasers is shown to be identical with that in continuous-wave CO2 lasers, except that the autodyne amplification during the laser pulse proves time-dependent. It is demonstrated that the amplitude-frequency characteristic of the autodyne amplification for PP CO2 lasers is also of resonance nature, but its bandwidth is broadened, as compared with that in the case of continuous laser pumping. As in the case of continuous pumping, the self-mixing effect in PP CO2 lasers can be used to detect and analyze backscattered signals, specifically for measuring the rates of destruction of materials by the 10 mu m radiation and for monitoring this process. (C) 2012 Optical Society of America