We investigate the possibilities for intracavity optothermal detection of microimpurities of gases. The generation regimes of a frequency-tunable wavequide CO-laser with an intracavity absorbing cell that contains NH3 and NO2 gases as absorbers are investigated experimentally. The conditions for stationary generation of such a laser are discussed. It is shown that the intracavity siting of the optothermal cell in a waveguide CO-laser makes it possible to increase the detecting ability of a gas analyzer by more than an order of magnitude as compared to the case of its external position. For NO2 and NH3 gases the magnitude of the minimum detected concentrations is ≈10 and 30 ppb, respectively.

Theoretical and experimental investigations were made of the reaction of the laser power to an external radiation signal. The laser with an injected signal (LIS) was an He—Ne laser emitting radiation at the wavelength of 3.39 μm in the form of two orthogonally polarised modes. A study was made of the influence of the frequency detuning of the external signal from the LIS radiation, and also of the intensities of both radiations on the laser power response.

For the first time an interaction has been studied experimentally between two linearly and orthogonally polarized modes in a waveguide CO2 laser emitting due to a separate vibration-rotational transition. A stable double-mode laser action has been obtained under the variation of the intermode distance from 0.3 to 140 MHz; the largest width of this region amounted to 180 MHz.

The first experimental investigation was made of the interaction of two linearly and orthogonally polarized modes in a waveguide CO2 laser utilizing an individual vibrational-rotational transition. Stable two-mode lasing was obtained when the mode separation was varied from 0.3 to 140 MHz. The greatest width of this region was 180 MHz.

A CO waveguide laser with radio-frequency excitation and working-medium cooling by thermoelectric converters is described. In a selective resonator with waveguide dimensions of 1.5 x 1.5 x 300 mm at a temperature of -17-degrees-C, generation is produced at almost-equal-to 90 CO-molecule transitions with an output power of up to 1.0 W in the wavelength range of 5.2-6.2-mu-m. The laser operates under sealed conditions and is cooled by water.

An analysis and comparison are carried out of selective properties of Case 1 waveguide resonators with reflectors placed near the waveguide and when one reflector is located at significant distance from the waveguide. Conditions are determined under which increased frequency and mode selectivities are realized in waveguide lasers with dispersive resonators. The "hard" selection of vibration-rotational transitions of 10P and 10R branches has been obtained experimentally in the waveguide CO2 laser. The continuous radiation frequency tuning range amounted to 750 MHz in this case for 18 transitions. Problems are considered which are related with modification of the transverse laser radiation intensity distribution for the substantial distance of the plane mirror from the waveguide.

The spectral properties of waveguide resonators having a configuration known as Case I are analyzed and compared when the reflectors are mounted directly next to the waveguide and when one of them is moved to a considerable distance from the waveguide. The conditions are determined under which the frequency and mode selectivities are increased in waveguide lasers with a dispersive resonator. Experiments are reported on a waveguide CO2 laser in which hard selection of the vibrational?rotational transitions of the 10P and 10R branches took place; the continuous tuning range of the radiation frequency for 18 transitions was then 750 MHz. A study was made of a change in the form of the transverse laser radiation intensity distribution when the plane mirror was removed to a considerable distance from the waveguide.

The use of waveguide CO(2) lasers having selective cavities to control the micro-admixtures in gas media is presented. Different laser signatures that can be applied in different gas analysis schemed depending on the degree of selectivity of the cavity are suggested. the results of measurement are given. The prospect application of such laser is discussed.

The operation of the waveguide CO(2)-laser, with an intracavity C(2)H(4)-absorption cell, has been studied experimentally and theoretically, by the offset of the laser frequency from the absorption center. It has been shown that there exist up to three offset areas within which the laser regimes are different: stable lasing, unstable lasing, and no radiation. The dependence of the frequency range of the areas of the absorption gas pressure has been obtained.

The paper considers the influence of the resonator parameters on the intensity distribution of a waveguide gas laser radiation. The experimental study of the waveguide CO2 laser beam profile confirms the theoretical predictions.

Breakdown of the sequence of active transitions in a waveguide CO2 laser occurred as a result of a change in the angle of inclination of a diffraction grating. This was accompanied by a change in the transverse distribution of the laser radiation intensity and was manifested at low rotational quantum numbers J. The observed effect was due to the characteristics of the frequency-selective losses in the selective waveguide resonator.