COMPARISON BETWEEN THE HE-NE LASER WAVELENGTH STANDARDS AT 633-NM FROM THE UME AND THE BIPM

An international comparison of the I-127(2) stabilized lasers, uses as wavelength standards and belonging to the National Metrology Institut e of Turkey (UME) and the Bureau des Poids et Mesures (BIPM), has been performed at the BIPM. A frequency stability of 45 Hz (a standard dev iation for a series of measurements over four days at an averaging tim e of about one hour), or 1 part in 10(13), has been achieved. This ind icates significant progress in the stabilization of this type of frequ ency standard and establishes a new level for international comparison s at 633 nm. The frequency difference between the UME and the BIPM sta ndards, which incorporate quite different laser components and iodine cells, has been found to be 0.7 kHz, much smaller than the reproducibi lity usually reported for this kind of laser standard. For the portabl e UME standard, the difference in frequencies found before and after t he comparison, when measured against a stationary UME laser, was less than 3 x 10(-13).