High-power repetitively pulsed CO2 laser with mechanical Q-switching and its application to studies in aerodynamic installations

A new method for organising the repetitively pulsed regime of CO₂ laser oscillation at the expense of a self-filtering resonator and two concave cylindrical mirrors with equal curvature in the intracavity modulator is considered. The studies of the energy and temporal characteristics of the laser radiation show that the constructed laser has high efficiency close to that of a cw laser. The mean and pulse power of 4.5 and 200 kW, respectively, are obtained. For a wide range of gas-dynamic characteristics the possibility of the optical breakdown in the supersonic wide-aperture air flow is demonstrated. The coefficient of absorption of laser radiation in optical breakdown plasma in a supersonic air flow is investigated and its value amounting to 60 % is obtained. For the first time it is found that the threshold density of air, corresponding to the efficiency jump, is equal to 1.8 — 2 kg m^-3 and independent of the Mach number M = 1.7 — 3.7.