Feasibility of narrow-line cooling in optical dipole traps

Grain, Ch.; Nazarova, T.; Degenhardt, C.; Vogt, Felix; Lisdat, Christian; Tiemann, E.; Sterr, U.; Riehle, F.

doi:10.1140/epjd/e2007-00052-6

Cited by 12 publications

(10 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[13] predicted the exceptionally small linewidth of 53 Hz, which explains our inability to detect the line with our current apparatus. This ultranarrow linewidth limits the transition's utility for a MOT, but along with the 741-nm line, the 1001-nm transition may be useful for resolved sideband cooling in an optical lattice [25][26][27]. This cooling technique may provide an alternative method [28] to evaporative cooling for the production of degenerate Dy gases.…”

Section: Alternative Laser-cooling Transitionsmentioning

confidence: 99%

Spectroscopy of a narrow-line laser-cooling transition in atomic dysprosium

Youn

Lev

2011

Phys. Rev. A

View full text Add to dashboard Cite

The laser cooling and trapping of ultracold neutral dysprosium has been demonstrated recently using the broad, open, 421-nm cycling transition. Narrow-line magneto-optical trapping of Dy on longer wavelength transitions would enable the preparation of ultracold Dy samples suitable for loading optical dipole traps and subsequent evaporative cooling. We have identified the closed 741-nm cycling transition as a candidate for the narrow-line cooling of Dy. We present experimental data on the isotope shifts, the hyperfine constants A and B, and the decay rate of the 741-nm transition. In addition, we report a measurement of the 421-nm transition's linewidth, which agrees with previous measurements. We summarize the laser-cooling characteristics of these transitions as well as other narrow cycling transitions that may prove useful for cooling Dy.

show abstract

Section: Alternative Laser-cooling Transitionsmentioning

confidence: 99%

Spectroscopy of a narrow-line laser-cooling transition in atomic dysprosium

Youn

Lev

2011

Phys. Rev. A

View full text Add to dashboard Cite

show abstract

“…Also intrinsic to the capability of the uv MOT to load atoms into the dipole trap is the ability to continue to laser cool on the uv transition in the optical trap, which is possible only if the differential AC Stark shift of the 2S 1/2 and 3P 3/2 states produced by the dipole trap light is sufficiently small [28,29]. Otherwise, the light shift would prevent uniform laser cooling in the trap, and depending on its sign, could even cause heating.…”

mentioning

confidence: 99%

“…Our results demonstrate that laser cooling on a narrow, but still dipole allowed, uv transition substantially increases the atom number and production rate of a quantum degenerate gas. Three features contribute to the success of this method: (1) the narrow linewidth gives lower temperatures, enabling trapping with lower optical trap depth, and hence, a larger trap volume for a given laser power; (2) the differential light shift at the trapping wavelength is both small and to the blue, which greatly enhances loading by permitting laser cooling to proceed in the presence of the optical trap [29]; and (3) the short wavelength cooling transition allows laser cooling to be effective even at higher densities. Since T R ≃ T D for the uv transition, the linewidth is sufficiently broad to avoid the need for either a spectrally-broadened source or a "quench" laser to effectively broaden an ultra-narrow transition by coupling it to a faster decaying excited state [16,17,29].…”

mentioning

confidence: 99%

“…Three features contribute to the success of this method: (1) the narrow linewidth gives lower temperatures, enabling trapping with lower optical trap depth, and hence, a larger trap volume for a given laser power; (2) the differential light shift at the trapping wavelength is both small and to the blue, which greatly enhances loading by permitting laser cooling to proceed in the presence of the optical trap [29]; and (3) the short wavelength cooling transition allows laser cooling to be effective even at higher densities. Since T R ≃ T D for the uv transition, the linewidth is sufficiently broad to avoid the need for either a spectrally-broadened source or a "quench" laser to effectively broaden an ultra-narrow transition by coupling it to a faster decaying excited state [16,17,29]. Additionally, since T D for the D2 line is only 7 times larger than T D for the uv transition, transfer from the red to uv MOT proceeds efficiently without the need of an intermediate cooling stage [15,18].…”

mentioning

confidence: 99%

See 1 more Smart Citation

All-optical production of a lithium quantum gas using narrow-line laser cooling

et al. 2011

View full text Add to dashboard Cite

We have used the narrow 2S 1/2 → 3P 3/2 transition in the ultraviolet (uv) to laser cool and magneto-optically trap (MOT) 6 Li atoms. Laser cooling of lithium is usually performed on the 2S 1/2 → 2P 3/2 (D2) transition, and temperatures of ∼300 μK are typically achieved. The linewidth of the uv transition is seven times narrower than the D2 line, resulting in lower laser cooling temperatures. We demonstrate that a MOT operating on the uv transition reaches temperatures as low as 59 μK. Furthermore, we find that the light shift of the uv transition in an optical dipole trap at 1070 nm is small and blueshifted, facilitating efficient loading from the uv MOT. Evaporative cooling of a two spin-state mixture of 6 Li in the optical trap produces a quantum degenerate Fermi gas with 3 × 10 6 atoms in a total cycle time of only 11 s. The creation of quantum degenerate gases using all-optical techniques [1-4] offers several advantages over methods employing magnetic traps. Optical potentials can trap any ground state, allowing selection of hyperfine sublevels with favorable elastic and inelastic scattering properties. In the case of Fermi gases, the ability to trap atoms in more than one sublevel eliminates the need for sympathetic cooling with another species [5,6], greatly simplifying the experimental setup. All-optical methods also facilitate rapid evaporative cooling since magnetically tunable Feshbach resonances can be employed to achieve fast thermalization.There are, however, challenges to all-optical methods. An essential prerequisite is an optical potential whose depth is sufficiently greater than the temperature of the atoms being loaded. The usual starting point is a laser cooled atomic gas confined to a magneto-optical trap (MOT). In a twolevel picture, atoms may be cooled to the Doppler limit T D =h /(2k B ), where /(2π ) is the natural linewidth of the excited state of the cooling transition [7,8]. In many cases, however, sub-Doppler temperatures can be realized due to the occurrence of polarization gradient cooling arising from the multilevel character of real atoms [9]. Polarization gradient cooling mechanisms are effective if the linewidth of the cooling transition is small compared to the hyperfine splitting of the excited state, or if there is a large degree of magnetic degeneracy in the ground state [10]. The limit to cooling in these cases is the recoil temperature T R =h 2 k 2 /(2mk B ), where k is the wave number of the laser cooling transition and m is the mass of the atom.Polarization gradient cooling is found to be efficient for most of the alkali-metal atoms including Na, Rb, and Cs; MOTs of these species routinely attain temperatures of ∼10 μK, which is not far above T R . Unfortunately, for Li and K, the elements most often employed in Fermi-gas experiments, sub-Doppler cooling is ineffective in the presence of magnetic fields, including those required for a MOT. For Li, sub-Doppler cooling is inhibited because the hyperfine splitting of the excited state is unresolved (Fig. 1), thus limiting ...

show abstract

“…Here the ac-Stark shifts due to the trapping laser for the ground state and one Zeeman component of the excited state 3 P 1 are equal [12]. In addition, it has to be assured that the transitions to the other Zeeman components are not shifted into resonance [13]. Choosing a high power laser with a wavelength of 1030 nm assures that all transitions are shifted away from resonance such that the cooling laser remains red detuned from all transitions.…”

mentioning

confidence: 99%

Bose-Einstein Condensation of Alkaline Earth Atoms:Ca40

et al. 2009

View full text Add to dashboard Cite

We have achieved Bose-Einstein condensation of 40 Ca, the first for an alkaline earth element. The influence of elastic and inelastic collisions associated with the large ground-state s-wave scattering length of 40 Ca was measured. From these findings, an optimized loading and cooling scheme was developed that allowed us to condense about 2·10 4 atoms after laser cooling in a two-stage magnetooptical trap and subsequent forced evaporation in a crossed dipole trap within less than 3 s. The condensation of an alkaline earth element opens novel opportunities for precision measurements on the narrow intercombination lines as well as investigations of molecular states at the 1 S-3 P asymptotes.PACS numbers: 03.75.Hh, 67.85.HjThe first Bose-Einstein condensate (BEC) of a dilute quantum gas in 1995 has opened completely new avenues in physics. In subsequent years this quantum degenerate state could be reached with different species (for a recent list of references see, e. g., [1]). By far most research has been performed on alkali atomic and molecular BECs apart from hydrogen, metastable helium, chromium, and ytterbium. So far, no member of the alkaline earth elements could be brought to quantum degeneracy despite considerable effort [2,3]. The alkaline earth elements have unique properties, e. g., their narrow intercombination transitions or their ground state without a magnetic moment. Due to the non-degenerate ground state in 40 Ca and in the other alkaline earth elements, the associated simpler molecule structure allows for more accurate investigations of collisions [4,5]. Moreover, the vanishing magnetic moment in the ground and excited state will allow for novel applications in atom interferometry not hampered by phase shifts due to magnetic fields. Calcium has a particularly large ground state scattering length that not only made it interesting but also difficult to realize a BEC.Calcium (like the other alkaline earth elements) shares these properties with ytterbium which has a similar electronic structure [6] but has a five hundred-fold larger line width of the 1 S 0 -3 P 1 intercombination transition. This 370 Hz line width at 657 nm made calcium for some time the optical frequency standard with the lowest uncertainty in the visible [7]. Both technologies, optical frequency metrology and the generation of a BEC, can now be combined for novel applications.In this letter we report on the preparation of a 40 Ca BEC. Starting point for our experiment is a magnetooptical trap (MOT) on the 1 S 0 -1 P 1 transition in the singlet system. The vanishing ground-state magnetic moment prevents sub-Doppler cooling of 40 Ca in a MOT. To cool the atoms further we use a second MOT stage on the narrow intercombination line 1 S 0 -3 P 1 allowing for temperatures in the MOT as low as 15 µK. For efficient cooling we increase the scattering rate of this transition by quenching the upper state [8]. During both MOT stages an optical dipole trap is overlapped with the MOT. In order not to interfere with the narrow line cooling we choo...

show abstract

Feasibility of narrow-line cooling in optical dipole traps

Cited by 12 publications

References 35 publications

Spectroscopy of a narrow-line laser-cooling transition in atomic dysprosium

Spectroscopy of a narrow-line laser-cooling transition in atomic dysprosium

All-optical production of a lithium quantum gas using narrow-line laser cooling

Bose-Einstein Condensation of Alkaline Earth Atoms:Ca40

Contact Info

Product

Resources

About