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 (τ_0.1 ~ 1 – 10 μs) pulses of 0.1 – 0.5 J energy at a wavelength in the range λ₀ = 4.9 – 6.5 μm. 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 τ_0.1, and of the spectral interval Δν 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 E_out and on the efficiency η. In the single-pulse regime (τ_0.1 = 5 μs) the efficiency was η ≈ 0.6% at λ₀ ~ 5.2 μm (near the maximum of the spectrum obtained in the free-running regime) and η ≈ 0.1% at λ₀ ~ 6.0 μm. 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 η ~ 0.6% and the total output energy was E_out ~ 0.5 J (the number of pulses in a series was M =8 , their duration was τ_0.1 = 5 μs, and the wavelength was λ₀ ~ 5.8 μm). At some wavelengths the values of η and E_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.