AN IMPROVED HE-NE-LASER AT LAMBDA= 612 NM, STABILIZED BY MEANS OF AN EXTERNAL ABSORPTION CELL

A He-Ne laser at lambda equals 612 nm, stabilized to saturated absorption features of **1**2**7I//2 in an external cell left bracket and with no cell inside the laser cavity right bracket is presented. The successive-2-sample deviation for an averaging time of 10 s is not larger than 0. 15 kHz or 3 multiplied by 10** minus **1**3 of the laser frequency. The uncertainty of the laser frequency due to variations of the laser power or of the beam geometry is less than 5 kHz. But dramatic frequency shifts occur when the returning beam touches an obstacle. Single and multiple linear-regression analyses of the pressure and modulation dependence seem to offer a measure of the reproducibility and of technical or physical perturbations.