He-Ne lasers stabilized by saturated absorption in iodine at 612 nm

The metrological potentials of two 612-nm He-Ne lasers stabilized by saturated absorption in iodine are compared. In the case of stabilization to an internal cell, the device easily produces high-contrast resonances but has some drawbacks such as a strong power broadening of the iodine lines, and the presence of weak parasitic lines. In the case of stabilization to an external cell, strong and narrow signals are obtained. This system is promising for an improvement of frequency stability and reproducibility.