Intercomparison of 127 I_2 stabilised 633 nm He-Ne lasers locked by 5th harmonic method

Project Description

An international comparison of the optical frequencies of 127 I_2 stabilised 5th harmonic locked He-Ne lasers at 633 nm will be arranged at Centre for Metrology and Accreditaion between 7th and 11th of September 1998. The recent research suggests that use of the 5th harmonic stabilisation would improve the frequency reproducibility and stability of iodine stabilized lasers locked by the 5th harmonic method.

Final Report 2000-04-07

An international comparison of 127 I_2-stabilised 633 nm He-Ne lasers locked either by the 5th or by the 3rd harmonic technique was carried out at the MIKES in September 1998. Participating laboratories were: the Centre for Metrology and Accreditation (MIKES); the Helsinki University of Technology, Metrology Research Institute (HUT); the National Institute of Metrology Beijing (NIM); the Czech Metrological Institute (CMI); the D.I. Mendeleyev Institute for Metrology (VNIIM); and the Bureau International des Poids et Mesures (BIPM).
The purpose of the comparison was to study the properties of the 5th harmonic locking technique against the 3rd, especially the frequency reproducibility and to confirm an earlier frequency shift measured relative to the 3rd harmonic locking technique. The results of the comparison exhibit a significantly lower gap for the frequency differences between lasers when using the 5th harmonic. It is clear that the use of the FHT allows a higher accuracy to be obtained for the stabilised frequency.
Comparison report is submitted to Metrologia:

A. Lassila, K. Riski, J. Hu, T. Ahola, S. Naicheng, L. Chengyang, P. Balling,J. Blabla, L. Abramova, Yu. G. Zakharenko, V.L. Fedorin, A. Chartier and J.-M. Chartier, International comparison of He-Ne lasers stabilized with 127I2 at λ ≈ 633 nm: Use of the FIFTH or the THIRD Harmonic-locking techniques compared.