Beam variations in a multiple-pass cavity

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Abstract
In order to measure ozone of the atmosphere by absorption, the authors reanalyse the Herriott multipass cell, composed of two concave mirrors with focal length f. They study particularly the influence of the different parameters upon the emergent light beam. As expected with such a cavity, angular variations of the mirrors are self corrected at least partially. Since the cavity is like a divergent mirror with focal length-f, this cavity increases the fluctuations of the incident beam. The variations of the distance d between mirrors as well as focal length f make a shift of the emergent beam. Nevertheless for a cavity with d=4 m and 50 passes, authorized angular variations of the emergent beam are of the order of a few minutes. Maximum relative variations of d and f of 310-4 are not great constraints.
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