Pulsed frequency-selective tunable Q-switched CO laser excited by an electron-beam-controlled discharge

A frequency-selective tunable Q-switched CO laser was constructed. It was excited by an electron-beam-controlled discharge and it emitted short (tau(0.1) similar to 1-10 mu s) pulses of 0.1-0.5 J energy at a wave-length in the range lambda(0) = 4.9-6.5 mu m. The pulse energy was sufficient to exert a force on absorbing materials. A study was made of the influence of the composition, density, and temperature of the laser mixture, of the pulse duration tau(0.1), and of the spectral interval Delta nu of the laser radiation on the output characteristics of this laser. A special optical system was developed for investigating the influence of suppression and 'locking' inside the cavity of various parts of the laser radiation spectrum on the output energy Q(out) and on the efficiency eta. In the single-pulse regime (tau(0.1) = 5 mu s) the efficiency was eta approximate to 0.6% at lambda(0) similar to 5.2 mu m (near the maximum of the spectrum obtained in the free-running regime) and eta approximate to 0.1% at lambda(0) similar to 6.0 mu M. Frequency-selective generation of a series of short pulses was the result of repeated Q switching during one pump pulse. In this case, the efficiency at the long-wavelength edge of the spectrum was eta similar to 0.6% and the total output energy was Q(out) similar to 0.5 J (the number of pulses in a series was M = 8, their duration was tau(0.1) = 5 mu s, and the wavelength was lambda(0) similar to 5.8 mu M). At some wavelengths the values of eta and Q(out) depended weakly on the temperature of the laser mixture in the range 100-150 K. The fine temporal structure of the laser pulses was investigated with nanosecond resolution.