Feasibiliy of improvement of the spatial spectrum of radiation from a cw chemical HF laser

Calculations are reported of the radiation field of a cw chemical HF laser with an unstable telescopic cavity in which a coupling mirror has a Gaussian reflectivity profile. Contribution of the vibrationally excited HF(υ) molecules to the refractive index of the gas is taken into account. It is shown that high-quality radiation with the divergence angle close to the diffraction limit can be generated in such a cavity. Stable generation of such radiation is possible also at low magnifications (provided that M ≥ 1.25), which ensures a high energy efficiency. At still lower magnifications the divergence increases considerably and the main contribution to the phase distortions comes from the HF(υ) molecules.