Abstract
This article deals with the evaluation of the chemical purity of iodine-filled absorption cells and the optical frequency references used for the frequency locking of laser standards. We summarize the recent trends and progress in absorption cell technology and we focus on methods for iodine cell purity testing. We compare two independent experimental systems based on the laser-induced fluorescence method, showing an improvement of measurement uncertainty by introducing a compensation system reducing unwanted influences. We show the advantages of this technique, which is relatively simple and does not require extensive hardware equipment. As an alternative to the traditionally used methods we propose an approach of hyperfine transitions’ spectral linewidth measurement. The key characteristic of this method is demonstrated on a set of testing iodine cells. The relationship between laser-induced fluorescence and transition linewidth methods will be presented as well as a summary of the advantages and disadvantages of the proposed technique (in comparison with traditional measurement approaches).
Highlights
The metrology of length and time is currently developing fast
We investigated the key properties and limits of possible measurement methods for the purity evaluation of iodine absorption cells and summarized the recommendations for testing these iodine evaluation of iodine absorption cells and summarized the recommendations for testing these iodine cells
We selected a set of iodine cells with different optomechanical designs and absorption media cells
Summary
The metrology of length and time is currently developing fast. While the definition of the second will most likely stay unchanged for some time (thanks to the significant improvement of the Cesium atomic clock), the unification of the fundamental metrology of time and length can be expected in the future. Optical frequency standards based on traditional spectroscopy in gaseous media may lose the status of the primary standards in the future. The complexity and price of optical clocks ensure their further utilization. There are numerous applications where the robustness, simplicity, cost and reliability together with a compact design play a key role. Examples of that are systems designed for airborne or even space-borne applications [7], optical telecommunications [8] or lasers for ballistic gravimeters [9]
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