Helium-neon laser stabilized by saturated absorption in iodine at 612 nm

Hyperfine structure of iodine has been studied at 612 nm by the technique of saturated absorption in an iodine cell placed in a He-Ne laser modified to operate at this wavelength. The most interesting feature of the laser is the existence of strong inverted Lamb dips at a very low vapor pressure, which provides very good short term frequency stability. Some factors which limit the reproducibility of the device are also investigated.