gas laser with an intracavity absorbing cell is studied experimentally and theoretically at a modulation frequency approximately equal to the intermode beat frequency. It is revealed that in the vicinity of the absorption-line centre the intensity of every mode for certain system parameters displays resonance structures narrower than the homogeneous line width of the absorption line. This occurs when the range of mode synchronization is near the absorption-line centre and its size is less than the homogeneous width of the absorption line.

The results are reported of the CO-laser optothermal (OT) detection of impurity gases when their absorption spectra overlap with those of an interfering gas. The influence of the latter was avoided using low gas pressures corresponding to a maximum of the OT sensitivity. Frequency tuned in the 5.2–6.3 μm wavelength range, 12C16O and 13C16O waveguide lasers were used. The fine frequency tuning at 490 MHz was achieved for 150 laser transitions of both molecules. The OT sensitivity was estimated by NO2 detection in the presence of water vapor. The minimal detectable concentration proved to be 60 ppb at P19–18(14) transition of a 12C16O laser for NO2 and 75 ppb on P12–11(13) transition of a 13C16O laser for H2O.

The results of the investigation of a rf-discharge-excited sealed-off CO waveguide laser with a selective resonator are reported. The operation on more than 40 vibration-rotation transitions of a CO molecule has been obtained in a laser having a square section (Al/BeO) waveguide with dimensions of 1.5×1.5×180 mm. Maximum frequency tuning of 550 MHz with output power of 0.5 W at line centre has been observed on theP10−9(17) transition at −20°C ground electrode temperature at a pressure of 180 Torr.

The present paper discusses a way of increasing the frequency tuning range in a CW RF excited waveguide CO2 laser by utilising a rectangular configuration of the waveguide cross-section. The substitution of 4He for 3He is also discussed. The frequency tuning range realized in the laser made approximately 970 MHz with the output power level 0.2 W and 0.04 W at the centre and maximum off-set frequency respectively.

A differential absorption method combined with heterodyne photodetection was used in a remote laser gas analyzer placed on board of an aircraft. A waveguide CO2 laser with alternate switching of lasing between the two nearest lines of the vibrational–rotational spectrum of CO2 was used as the light source. The gas analyzer was placed on board a helicopter and was used to localize a simulated escape of the gas from an ammonia pipeline and to estimate the amount of ammonia released as an effluent.

The results of experimental and theoretical investigations of optothermal detector characteristics are presented. The experimental dependence of the optothermal signal amplitude and phase vs the absorption gas pressure and the chopper frequency of the gas exciting laser radiation are reported. The suggested model, considering two main energy transfer mechanisms in the optothermal detector (heat conductivity and fluorescence), is in good agreement with the experimental results.

The present paper suggests and discusses a method allowing one to produce a two-frequency switching mode between any two adjacent transitions of a CO2 laser. Switching is achieved by means of simple modulation of the resonator length by a piezoelement. The use of conventional electronic circuits ensures the maintainance of a high power balance (10−2–10−1%) vs. switching rate) at the generation frequencies. The data of the two-frequency CO2 laser with a waveguide resonator used for various systems, based on a differential absorption technique and designed to control the atmospheric pollutions, are presented.