Stabilization of the emission frequency of a carbon dioxide laser by an external nonlinearly absorbing SF6 cell

A description is given of a method for the stabilization of the emission frequency of a CO₂ laser based on the use of narrow resonances in the absorption line of an external molecular (SF₆) low-pressure cell operated under saturation absorption conditions. The relative stability of the frequencies of two independently stabilized CO₂ lasers was 3·10^–11 in 10 min. The upper limit of the collision-induced frequency shift was determined for a vibration-rotational transition in the SF₆ molecule: This shift did not exceed 300 Hz/mtorr. An analysis was made of the effects influencing the frequency instability under experimental conditions and methods for improving the stability and reproducibility of the laser frequency were considered.