Calibrating an interferometric laser frequency stabilization to MHz precision

We report on a calibration procedure that enhances the precision of an interferometer based frequency stabilization by several orders of magnitude. For this purpose the frequency deviations of the stabilization are measured precisely by means of a frequency comb. This allows to implement several calibration steps that compensate different systematic errors. The resulting frequency deviation is shown to be less than $5.7 $MHz (rms $1.6 $MHz) in the whole wavelength interval $750 - 795 $nm. Wide tuning of a stabilized laser at this exceptional precision is demonstrated.