The mid-IR cw tunable solid state two-mode Cr2+:ZnSe laser with intracavity methane cryocell was developed. The laser was applied for sub-Doppler spectroscopy of (υ1+υ4) vibrational-rotational band of methane and observation of narrow resonances of saturated dispersion at λ = 2.36 μm. The new technique of low pressure methane gas cooling was used instead of liquid nitrogen “jacket” design applied in our previous work. Parameters of saturated dispersion resonances were estimated in 77-300 K temperature range. The experiments confirmed that laser with the new “dry cooled” methane cell has prospectives for reaching a short-term frequency stability at the level of 10-15-0-16 and can be used as a compact device.

The shifts of centres of nonlinear absorption and dispersion resonances in lasers with an internal absorbing cell are described. The shifts are caused by parasitic reflection of light from an intracavity plate and oscillate depending on the plate position. It is shown that this reflection leads to losses oscillating depending on the plate position. The main reasons of shifts in this case are frequency modulation used for laser frequency stabilisation and the curvature of the gain line in the two-mode regime. The results of a model experiment agree with theoretical estimates.

Results of absolute frequency calibration of the He-Ne/CH4 Transportable Optical Frequency Standard (TOFS) and intercomparisons the TOFS with CO2/OsO4 OFS carried out on 1996 - 1997 in collaboration of three organizations (Lebedev Institute, PTB, and BNM-LPTF) are reported.

This paper presents the results of a research work about the infrared optical frequency standars (OFS) done at the Lebedev Physics Institute. The standards are based on methane stabilized He-Ne lasers which are found to be a very stable source in the optical region. The results of the frequency comparisons of the two He-Ne/CH_{4} OFS with the typical homogeneous width of the reference lines in the range from 7 kHz to 700 Hz are given. The results show that the reproducibility of the investigated lasers can be estimated from 3.10^{-13} to 1.10^{-13} in dependence with the width of the reference line used.

Results of absolute frequency measurements carried on at PTB in the 1995 year with transportable HeNe/CH/sub 4/ laser (Lebedev Institute, Moscow) stabilized over the resolved magnetic hyperfine structure (MHPS) of F/sup (2)//sub 2/ methane line (/spl lambda/=3.39 /spl mu/m) are presented.

A tunable colour-centre laser was used in a study of Doppler-free saturated absorption resonances at the R lines of the ν3 band of the methane molecule (λ = 3.2–3.3 μm). The spectral resolution was 300 kHz for a configuration with an intracavity absorption cell. The laser is suitable for the investigation of any of the R and Q lines of the ν3 methane band, and the long-wavelength limit of the tuning range reached the P(2) line.

Experimental and theoretical studies were made of the influence of a weak axial transverse magnetic field on the frequency shifts of a two-mode He–Ne/CH4 laser (λ = 3.39 μm) stabilized using narrow saturated dispersion resonances in the radiation frequency. In some cases a magnetic field applied to the laser active medium eliminated the asymmetry of the frequency resonances observed when the centers of the gain profile (ω0( + )) and the absorption line (ω0( – )) did not coincide. At ω0( + ) ≈ ω0( – ), the magnetic field does not influence the profile of the frequency resonances or the laser frequency shifts.

An analysis is made of the possibility of utilizing resonance photodissociation of van der Waals complexes (with a binding energy of <0.1 eV per molecule), and resonance desorption and acoustodesorption of adsorbed molecules bound to the surface by the weak van der Waals interaction in generating fluxes of cold atoms and molecules.