Inhomogeneity effects in a gas laser

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Abstract
We show that in a gas laser the inhomogeneity in the distribution of amplifying atoms and the transverse Gaussian distribution of the saturating electromagnetic field give rise to different lens effects which are generally opposite to each other and influence the line shapes in different ways, shifting the Lamb dip either to the blue or to the red. For those laser phenomena which increase one or the other of the lens effects, the role of a diaphragm is of particular importance, since it determines the spatial distribution of the resonant field. We present here a new method for studying the resonant diffracted field in a laser. Also, we give a unified description of the various inhomogeneities. Doing away with the usual method of mean-field approximation, we numerically calculate, for a diaphragmed, monomode weak-gain gas laser, the intensity, variation of the beam diameter, and the radius of curvature as functions of the frequency.