A PORTABLE IODINE STABILIZED HE-NE-LASER AND ITS USE IN AN ABSOLUTE GRAVIMETER

A portable, robust, and easy to use iodine-stabilized laser operating at a wavelength of 633 nm has been realized at the BIPM. The size of the laser and its electronic servo are such that they can be installed in a suitcase having dimensions acceptable in an aircraft cabin as hand baggage. The performance of this laser is comparable to that of stationary lasers. A frequency repeatability of a few parts in 10(11) and a frequency stability that can reach 2 parts in 10(13) on a 300 s sample time have been achieved. The radiation emitted by the laser can be used as a reference for optical interferometry for several years without the need for periodic calibration and its life is limited by that of the laser tube. A prototype has been installed in an absolute gravimeter and continuous sets of g measurements extending over more than thirty-hour periods have been achieved with standard deviations on the average value of g of about 2.5 parts in 10(8).