Efficient repumping of a Ca magneto-optical trap

We investigate the limiting factors in the standard implementation of the Ca magneto-optical trap. We find that intercombination transitions from the 4s5p0.16em0ex¹P₁ state used to repump the electronic population from the 3d4s0.16em0ex¹D₂ 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 ~20 times and ~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 3d4s0.16em0ex¹D₂ state, yielding a trap lifetime of ~5 s.