Molecular laser stabilization at low frequencies for the LISA mission

Abstract

We have developed a 532~nm iodine stabilized laser system that may be suitable for the LISA mission (Laser Interferometer Space Antenna) or other future spaceborne missions. This system is based on an externally frequency-doubled Nd:YAG laser source and uses the molecular transfer spectroscopy technique for the frequency stabilization. This technique has been optimized for LISA: compactness (less than 1.1\ifmmode\times\else\texttimes\fi{}1.1\,\,m2), vacuum compatibility, ease of use and initialization, minimization of the number of active components (acousto-optic modulators are both used for frequency shifting and phase modulating the pump beam). By locking on the a10 hyperfine component of the R(56)32-0 transition, we find an Allan standard deviation ($\sigma${}) of 3\ifmmode\times\else\texttimes\fi{}10-14 at 1~s and $\sigma${}<2\ifmmode\times\else\texttimes\fi{}10-14 for 20\,\,s$\le${}$\tau${}$\le${}103\,\,s. In terms of linear spectral density, this roughly corresponds to a stability better than 30\,\,Hz/Hz between 10-2 and 1~Hz with a stability decrease close to 1/f below 10~mHz.