Influence of a gas lens on the profile of a narrow resonance in a cell and in an interferometer

A theoretical investigation is reported of the influence of self-focusing of Gaussian beams on the profile of a saturated absorption resonance in laser frequency standards. An analysis is made of systems with an external nonlinearly absorbing cell and an external interferometer containing a nonlinear absorber. Analytic relationships for the profile of an asymmetric resonance and a shift of its maximum in the course of local and integral photodetection of an optical beam are derived on the assumption of weak absorption and saturation.