We demonstrate an efficient scheme for continuous trap loading based upon
spatially selective optical pumping. We discuss the case of 1S0​
calcium atoms in an optical dipole trap (ODT), however, similar strategies
should be applicable to a wide range of atomic species. Our starting point is a
reservoir of moderately cold (≈300μK) metastable
3P2​-atoms prepared by means of a magneto-optic trap (triplet-MOT). A
focused 532 nm laser beam produces a strongly elongated optical potential for
1S0​-atoms with up to 350 μK well depth. A weak focused laser beam
at 430 nm, carefully superimposed upon the ODT beam, selectively pumps the
3P2​-atoms inside the capture volume to the singlet state, where they
are confined by the ODT. The triplet-MOT perpetually refills the capture volume
with 3P2​-atoms thus providing a continuous stream of cold atoms into
the ODT at a rate of 107s−1. Limited by evaporation loss, in 200 ms we
typically load 5×105 atoms with an initial radial temperature of 85
μK. After terminating the loading we observe evaporation during 50 ms
leaving us with 105 atoms at radial temperatures close to 40 μK and a
peak phase space density of 6.8×10−5. We point out that a
comparable scheme could be employed to load a dipole trap with
3P0​-atoms.Comment: 4 pages, 4 figure