Narrow-line cooling of 87Rb using 5S1/2 → 6P3/2 open transition at 420 nm


 Magneto-optical trap (MOT) at narrow transition offers lower temperature and hence is the key for producing high phase density atomic cloud and subsequently quantum degeneracy with a large number of atoms for many elements. In this paper, we describe the loading of 87Rb atoms in the MOT using a narrow open transition (5S1/2 → 6P3/2) at 420 nm (i.e. blue MOT) from the routinely implemented MOT using a broad cyclic transition (5S1/2 → 5P3/2) at 780 nm (i.e. IR MOT). Using the four times narrower transition, we have trapped around 108 atoms in the MOT with a typical temperature of around 54 µK. We have also studied the behavior of the blue MOT with various parameters such as hold time, detuning, and power of trapping and repumper beams.