Laser-induced fluorescence as a tool to verify the reproducibility of iodine-based laser standards: a study of 96 iodine cells

We have validated the laser-induced fluorescence technique to measure the quality of iodine cells whose transitions are used as a reference in laser standards for the realization of the definition of the metre. In this technique, the change in induced fluorescence is measured for different values of iodine pressure in the cell: for an iodine cell contaminated with foreign gases the fluorescence is more sensitive to iodine pressure changes than for a pure one due to collisional quenching of the excited states. We have measured the fluorescence parameter K-o for a total of 96 iodine cells, and for each cell we correlated K-o with the measured absolute frequency when the cell is inserted into laser standards at wavelengths 515 nm, 532 nm and 633 nm. We observed that the distribution of the quality of the produced iodine cells has a large dispersion and we believe that this also significantly affects the frequency distribution of the iodine-based laser standards that are used to realize the definition of the metre.