Quenched narrow-line laser cooling of calcium-40 with application to an optical clock based on ultracold neutral calcium atoms

Stephen Rupper, Scott Bergeson

Norris, Ian

Tatiana Nazarova, C. Degenhardt, Christian Lisdat +3 more

E. A. Curtis, Chris W. Oates, Leo W. Hollberg

We present a cooling method that should be generally applicable to atoms with narrow optical transitions. This technique uses velocity-selective pulses to drive atoms towards a zero-velocity dark state and then quenches the excited state to increase the cooling rate. We demonstrate this technique of quenched narrow-line cooling by reducing the 1D temperature of a sample of neutral ${}^{40}\mathrm{Ca}$ atoms. We cool selected velocities with the ${}^{1}{S}_{0}{(4s}^{2}{)}^{3}{P}_{1}(4s4p)$ 657-nm intercombination line and quench with the ${}^{3}{P}_{1}{(4s4p)}^{1}{S}_{0}(4s5s)$ intercombination line at 553 nm, which increases the cooling rate eightfold. Limited only by available quenching laser power, we have transferred 18% of the atoms from our initial 2-mK velocity distribution and achieved temperatures as low as 4 \ensuremath{\mu}K, corresponding to a ${v}_{\mathrm{rms}}$ of 2.8 cm/s or 2 recoils at 657 nm. This cooling technique, which is closely related to Raman cooling, can be extended to three dimensions.

E. A. Curtis, Chris W. Oates, Leo W. Hollberg

Summary form only given. We are presently investigating various schemes for quenched cooling in 3D, which should give sub-recoil temperatures and higher transfer efficiencies. Such samples should produce significant improvement in the performance of optical frequency standards as well as open the door to other applications, enabling efficient loading of dipole traps and higher phase space densities.

Uwe Sterr, C. Degenhardt, Hardo Stoehr +6 more