Isotope dependence of gas laser intensity profiles.

We describe first the single mode output intensity of a Brewster windowed laser containing isotope mixtures when the cavity tuning is varied, and then the single mode output of a non-Brewster windowed laser under the influence of an axial magnetic field (Zeeman laser). We show how the central tuning (Lamb) dip in intensity gives way to more complicated tuning dependences such as a double dip. For axial magnetic fields, the isotope mixtures lead to slightly asymmetric gain curves and different intensity profiles under magnetic tuning. The discussion is based on an extension of a fundamental laser theory by Lamb, with special reference to the general work on the Zeeman laser by Sargent, Lamb, and Fork, in which the theory necessary to handle isotope mixtures was given in detail, although numerical calculations were reported only for single isotope media. In our numerical calculations, we have used parameters appropriate for the He-Ne gas laser operating in the red (632.8 nm).