A mid-infrared magneto-optical trap of metastable strontium for an optical lattice clock

Abstract

We report on the realization of a magneto-optical trap (MOT) for metastable strontium operating on the 2.92 $\hat{I}¼$m transition between the energy levels $5s5p{}^3{\mathrm{P}}_2$ and $5s4d{}^3{\mathrm{D}}_3$. The strontium atoms are initially captured in a MOT operating on the 461 nm transition between the energy levels $5s^2{}^1{\mathrm{S}}_0$ and $5s5p{}^1{\mathrm{P}}_1$, prior to being transferred into the metastable MOT and cooled to a final temperature of 6 $\hat{I}¼$K. Challenges arising from aligning the mid-infrared and 461 nm light are mitigated by employing the same pyramid reflector to realize both MOTs. Finally, the 2.92 $\hat{I}¼$m transition is used to realize a full cooling sequence for an optical lattice clock, in which cold samples of ${}^{87}\mathrm{Sr}$ are loaded into a magic-wavelength optical lattice and initialized in a spin-polarized state to allow high-precision spectroscopy of the $5s^2{}^1{\mathrm{S}}_0$ to $5s5p{}^3{\mathrm{P}}_0$ clock transition.