Narrow-line magneto-optical trap for erbium

We report on the experimental realization of a robust and efficient magneto-optical trap for erbium atoms, based on a narrow cooling transition at 583 nm. We observe up to $N=2\times {10}^8$ atoms at a temperature of about $T=15$ $\mu$K. This simple scheme provides better starting conditions for direct loading of dipole traps as compared to approaches based on the strong cooling transition alone, or on a combination of a strong and a narrow kHz transition. Our results on Er point to a general, simple, and efficient approach to laser cool samples of other lanthanide atoms (Ho, Dy, and Tm) for the production of quantum-degenerate samples.

Figure 1

Energy levels of atomic erbium up to $25000$ cm${}^{-1}$ for different total electronic angular momentum quantum numbers $J$ [21]. States with odd (even) parity are indicated by black (red/gray) horizontal lines. The two relevant laser cooling transitions at 401 and 583 nm are indicated by arrows [22].

Figure 2

Loading (a) and decay (b) of the narrow-line MOT with ${}^{166}$Er atoms for ${\delta }_{583}=-50{\Gamma }_{583}$ (circles) and ${\delta }_{583}=-32{\Gamma }_{583}$ (triangles). (a) Atom numbers are plotted as a function of the MOT loading time. The solid lines are fits to the data using $N\left(t\right)=N_{\mathrm{ss}}(1-e^{-\gamma t})$ with $N_{\mathrm{ss}}=R/\gamma$. From the fits we obtain $\gamma =0.137\left(2\right)$ s${}^{-1}$, $R=2.6\left(4\right)\times {10}^7$ s${}^{-1}$, and $\gamma =0.200\left(4\right)$ s${}^{-1}$, $R=1.1\left(1\right)\times {10}^7$ s${}^{-1}$ for $-50{\Gamma }_{583}$ and $-32{\Gamma }_{583}$, respectively. The inset shows the atom number after 10-s loading time as a function of the MOT detuning. (b) Atom numbers are plotted as a function of the holding time in the MOT in presence (open symbols) and absence of the ZS light (solid symbols). The solid lines are fits to the data using a double-exponential function; see text.

Figure 3

Behavior of different Er isotopes. (a) MOT atom number for the four most abundant bosonic isotopes as well as for the ${}^{167}$Er fermionic isotope is plotted as a function of the natural abundance for 20-s (squares) and 5-s (circles) loading times. (b) Spectroscopy signal of the blue transition shows the isotope shifts for the bosonic isotopes and the HF structure of ${}^{167}\mathrm{Er}$. The arrow indicates the locking point used for the ZS light to produce the ${}^{167}\mathrm{Er}$ MOT.