Laser Cooling of Erbium Atoms
Figure 1. A 401-nm laser beam (traveling from left to right) slows erbium atoms as the emerge from
an oven at 1300°C.
Motivated by a desire to expand our capabilities in making deterministic sources of atoms with a range of technologically significant species, we are investigating laser cooling of erbium atoms. Erbium is primarily interesting because of its optical properties as a rare earth dopant - a deterministic source of erbium atoms could lead, for example, to controlled fabrication of novel single-atom photonic devices. Our studies have revealed, though, that erbium also has unique laser cooling properties that could lead to advances in quantum optics, quantum degenerate gases, cold collision studies, and atomic clocks.
The atomic energy level structure of erbium is complicated, with a 3H6 ground state and many low-lying levels formed by various configurations of the n = 4, 5 and 6 shells. However, from a laser cooling perspective, of primary interest are J → J + 1 optically allowed transitions with no (or nearly no) optical leaks to metastable levels. We have identified five such transitions, all of which can be accessed with common tunable lasers.
Figure 2. Energy levels of atomic erbium, showing five laser cooling transitions at
wavelengths of 1299 nm, 841 nm, 631 nm, 583 nm, and 401 nm.
(click on figure
for a larger version)
To determine the laser cooling parameters for the identified transitions, several of which have not been investigated before, we have carried out measurements and calculations of the transition rates [EPG Pub #761]. The resulting values suggest some exciting possibilities for new experiments. For example, the 401 nm transition, with its short lifetime of 5.8 ns, is ideally suited for rapidly slowing and trapping large populations of cold atoms. The 841 nm transition, on the other hand, can be used with simple polarization-gradient laser cooling to cool atoms close to a recoil temperature of 80 nK - the coldest recoil temperature found in any atom so far. The 1299 nm transition is especially interesting because its wavelength falls in a standard telecom wavelength range, opening possibilities for new quantum communication schemes. Research on these and other topics is ongoing, with the first step of creating an erbium magneto-optical trap using 401 nm laser light already accomplished.
| Laser cooling parameter |
Transition (listed by vacuum wavelength) | ||||
|---|---|---|---|---|---|
| 400.91 nm | 582.84 nm | 631.04 nm | 841.22 nm | 1299.21 nm | |
| Γ | 1.7x108 s-1 | 1.0x106 s-1 | 1.8x105 s-1 | 5.0x104 s-1 | 13±7c s-1 |
| τ | 5.8 nsa | 0.96 µsa | 5.6 ± 1.4 µsb | 20 ± 4 µsb | 75 ms |
| Δυ | 27 MHz | 0.17 MHz | 28 kHz | 8.0 kHz | 2.1 Hz |
| Isat | 560 W m-2 | 1.1 W m-2 | 0.15 W m-2 | 18 mW m-2 | 13 µ W m-2 |
| vcapture | 11 m s-1 | 0.97 m s-1 | 18 mm s-1 | 6.7 mm s-1 | 2.8 µm s-1 |
| TDoppler | 660 µK | 4.0 µK | 680 nK | 190 nK | 51 pK |
| vDoppler | 0.18 m s-1 | 14 mm s-1 | 5.8 mm s-1 | 3.1 mm s-1 | 50 µm s-1 |
| Trecoil | 350 nK | 170 nK | 140 nK | 81 nK | 34 nK |
| vrecoil | 5.9 mm s-1 | 4.1 mm s-1 | 3.8 mm s-1 | 2.8 mm s-1 | 1.8 mm s-1 |
| a Literature value b Present work (experiment) c Present work (calculation) | |||||
Laser Cooling Transitions in Atomic Erbium
Jabez J. McClelland - NIST
James Hanssen - University of Maryland
Han Y. Ban - University of Pennsylvania
Marcus Jacka - University of York, UK
Joseph Reader - NIST
Online: September 2005
Last Updated: February 2008
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