Secondary laser cooling and capturing of thulium atoms in traps

Secondary laser cooling has been realised on the weak dipole transition 4f¹³(²F^o)6s², J = 7/2, F = 4 → 4f¹²(³H₆) 5d_5/26s², J' = 9/2, F' = 5 with the wavelength of 530.7 nm and natural width of 350 kHz. The temperature of the atomic cloud in a magnetooptical trap (MOT) was 30 μK at the lifetime of 2 s and the number of atoms 10⁵. Approximately 1% of atoms from the MOT have been reloaded to an optical dipole trap and to one-dimensional optical lattice at the wavelength of 532 nm. The atom lifetime in the optical lattice was 320 ms. We propose to employ thulium atoms captured in an optical lattice as an optical frequency reference.