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 was 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 10¹¹ and a frequency stability that can reach 2 parts in 10 ¹³ on a 300-s sample time are 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 was installed in an absolute gravimeter and continuous sets of g measurements extending over more than 30-h periods were achieved with standard deviations on the average value of g of about 2.5 parts in 10 ⁸