Frequency shifts in iodine stabilized lasers

Abstract

Stabilized He-Ne lasers commonly use the zero crossing of the third harmonic of a hyperfine absorption feature of iodine as a reference frequency. The zero crossing is affected by the Lorentzian tails of neighbouring absorption features. As a result the laser frequency becomes a function of modulation amplitude, laser power and iodine vapour pressure of the absorption cell. The magnitude of the frequency shifts so obtained are evaluated and discussed.