Laser standards for interferometry and stable frequencies distribution

Optical frequency references - absorption cells - represent an unique tool for frequency stabilization of the laser sources. Their spectral properies define overall quality of the stabilized laser, so these properties must be precisely controlled and verified. One of the most used absorption media in the visible spectral range is molecular iodine. It offers wide and reach spectra of very narrow and strong transitions so many types of laser standards can be realized on base of this media. Testing of final properties of iodine absorption cells is traditionaly based on two methods - laser induced fluorescence method (LIF) and evaluation of absolute frequency shifts of the iodine stabilized laser (beatnote measurement). Unfortunately both of these methods have few limitations and disadvantages - in case of high-quality cells the LIF method reaches its resolution limits, the beatnote method needs quite complicated optical setup. We present a novel approach for the iodine cells quality evaluation based on measurement of hyperfine transition linewidths - the impurities in absorption media cause line broadening of the transitions. Pilot measurement shows that presented method achieves a very good sensitivity to the iodine purity and together with a need of relatively simple setup can be considered as a novel method for absorption cells quality verification