Frequency stability and reproducibility of iodine stabilised He-Ne laser at 633 nm

The frequency of a 633 nm He-Ne laser is stabilised on a hyperfine-structure-component of natural iodine vapour. The third harmonic component of an applied modulation frequency is detected and a servosystem is used to lock the laser frequency to the zero-crossing of the third harmonic component. The stability and the reproducibility of the laser are determined by beat frequency experiment.