Influence of iodine cell quality onto the stability and absolute frequency shifts of laser etalons

Abstract

Frequency doubled Nd:YAG lasers are often the option with stabilization to the saturated absorption in molecular iodine featuring good signal-to-noise ratio at the 532 nm. Purity of iodine in the absorption cell is one of the most important factor how to achieve results in optical frequencies corresponding to theoretical values. We present results of measurement of purity of sets of iodine cells made at our institute. The purity was tested by improved method based on measurement of induced fluorescence and evaluation by the Stern-Volmer formula. Frequency-doubled Nd:YAG lasers stabilized with these cells were compared to evaluate their frequency shifts. The absolute frequencies of selected iodine hyperfine transitions were measured in direct laser frequency comparison with the reproducibility well below the kHz level. The results indicating the iodine cell purity are presented with relation to the absolute frequency shifts. This not only highlights the influence of iodine cell quality onto the stability and absolute frequency of lasers etalons but also shows the way towards improvements of the iodine cell manufacturing technology.