V N Bel'tyugov

Waveguide gas lasers with frequency-selective cavities

Frequency-selective cavities of waveguide gas lasers are investigated theoretically and experimentally. The problem of finding the field distribution and the radiation loss in a cavity with a diffraction grating is solved theoretically in general form. Frequency-selective properties are determined experimentally for certain particular configurations of waveguide (single-mode, with flat reflectors near the ends, nonselective) and open cavities. The calculations and experimental results agree. It is shown that the selectivity of a waveguide cavity has a nonmonotonic dependence on the length and diameter of the waveguide channel, so that the selectivity can be made several times better. The influence of the capillary wall material and of the location of the reflectors on the frequency properties of the cavity is analyzed. For the case with EH11 mode filtration, a method of accuracy not worse than 1.5% is developed for the analytic calculation of the losses. A cavity with a reflecting interferometer made up of a diffraction selector and a diffraction grating is proposed. It is shown experimentally and theoretically that its use permits separation of any (including sequential) transition from the emission spectrum of a CO2 laser and of longitudinal cavity modes.