Optimal design of dipole potentials for efficient loading of Sr atoms

We propose and demonstrate a novel far-off-resonance optical dipole trap (FORT) that is compatible with Doppler cooling. Strontium atoms are magneto-optically cooled and trapped by the spin-forbidden transition S-1(0) - P-3(1) at 689nm,while the tight-focused infrared laser couples these two states to the respective dipole-allowed singlet and triplet states to generate the same amount of light shift. These designed light shifts or the cooling transition, enabling simultaneous Doppler cooling and dipole trapping, lead to the efficient loading of cooled atoms into the FORT with a few recoil energies. This scheme provides an important step towards the realization of quantum degenerate strontium atoms by purely optical means.