Efficient repumping of a Ca magneto-optical trap

Abstract

We investigate the limiting factors in the standard implementation of the Ca magneto-optical trap. We find that intercombination transitions from the $4s5p{\phantom{\rule{0.16em}{0ex}}}^{1}{P}_{1}$ state used to repump the electronic population from the $3d4s{\phantom{\rule{0.16em}{0ex}}}^{1}{D}_{2}$ state severely reduce the trap lifetime. We explore seven alternative repumping schemes theoretically and investigate five of them experimentally. We find that all five of these schemes yield a significant increase in the trap lifetime and consequently improve the number of atoms and peak atom density by as much as $\ensuremath{\sim}20$ times and $\ensuremath{\sim}6$ times, respectively. One of these transitions, at 453 nm, is shown to approach the fundamental limit for a Ca magneto-optical trap with repumping only from the dark $3d4s{\phantom{\rule{0.16em}{0ex}}}^{1}{D}_{2}$ state, yielding a trap lifetime of $\ensuremath{\sim}5$ s.