Search

This paper presents the progress made to improve and develop the Bureau International des Poids et Mesures (BIPM) watt balance during the last two years. A reduction by a factor of five of the type A uncertainty was achieved by refining the velocity measurement. The BIPM simultaneous weighing and moving approach was experimentally compared to a bifilar coil technique. The relative difference to the Planck constant determination between the two approaches is 2 \times 10^-7 with a type A uncertainty of 3 \times 10^-7. A vacuum enclosure located in a dedicated laboratory with better thermal and vibrational isolation is ready to receive the present apparatus for further improvement. [ABSTRACT FROM PUBLISHER]

The generation of optical frequency combs, directly referenced to the SI second, can be used to make measurements of optical frequencies. This provides a supreme method for the realization of the meter. However, an approximate knowledge of the frequency of the radiation is normally needed for such measurements in order to determine the integral order of the comb component used. Such information is usually obtained by prior wavelength measurements of the radiation under study. This paper demonstrates a new method to determine the absolute mode number in optical frequency measurements using mode-locked femtosecond lasers, thus eliminating the need for complementary wavelength measurements. Measurements of the frequency of an iodine-stabilized He-Ne laser at λ=633 nm and a Nd:YAG laser at λ=532nm are given as examples. [ABSTRACT FROM PUBLISHER]

Presents results from comparisons at the International Bureau of Weights and Measures (BIPM) providing a world-wide reference network of [sup127]I[sub2] stabilized frequency-doubled neodymium (Nd): yttrium aluminium garnet (YAG) lasers. Selected working parameters for six lasers involved in the BIPM comparison; Overview of world-wide network of iodine-stabilized Nd:YAG lasers; Conclusion.