Comparison between 403 nm and 497 nm repumping schemes for strontium magneto-optical traps

Abstract

The theoretical description of the external degrees of freedom of atoms trapped inside a magnetooptical trap (MOT) often relies on the decoupling of the evolution of the internal and external degrees of freedom. That is possible thanks to much shorter timescales typically associated with the first ones. The electronic structure of alkaline-earth atoms, on the other hand, presents ultra-narrow transitions and metastable states that makes such an approximation invalid in the general case. In this article, we report on a model based on open Bloch equations for the evolution of the number of atoms in a magneto-optical trap. With this model we investigate the loading of the strontium blue magnetooptical trap under different repumping schemes, either directly from a Zeeman slower, or from an atomic reservoir made of atoms in a metastable state trapped in the magnetic quadrupolar field. The fluorescence observed on the strong 461 nm transition is recorded and quantitatively compared with the results from our simulations. The comparison between experimental results and calculations within our model allowed to identify the existence of the decay paths between the upper level of the repumping transition and the dark strontium metastable states, which could not be explained by electric dipole transition rates calculated in the literature. Moreover, our analysis pinpoints the role of the atomic movement in limiting the efficiency of the atomic repumping of the Sr metastable states.

Construction of an experiment providing cold strontium atoms for atomic interferometry in a ring cavity

“…This blue MOT collects 1.8 × 10 5 atoms approximately. As expected, this result is comparable with those obtained by other groups 43,44 and differs by being only one order of magnitude smaller. The Fig.…”

Novel repumping on $^{3}$P$_{0}$$\rightarrow$$^{3}$D$_{1}$ for Sr magneto-optical trap and Landé g factor measurement of $^{3}$D$_{1}$

“…The intensity of 19 mW/cm 2 for 461 nm laser results in B = 3.8 × 10 7 s −1 . The loss rate of Γ d is added to all levels involved in repumping that are dark for the cooling light [29]. The value for which can be deduced from the fit to experimental data.…”

An extended-cavity diode laser at 497 nm for laser cooling and trapping of neutral strontium

“…Vladimir Schkolnik · Oliver Fartmann · Markus Krutzik Humboldt-Universität zu Berlin, Newtonstr. 15,12489 Berlin, Germany E-mail: vladimir.schkolnik@physik.hu-berlin.de Currently the best performing optical clocks are based on neutral atoms trapped in a magic wavelength optical lattice [11]. In particular, clocks based on neutral strontium have become widely used over the world in the past, operating uninterrupted over multiple weeks in laboratories and recently started to even perform outside the lab [12].…”

“…and the 3 P 0 → 3 S 1 transition at 679 nm. Alternatively, only a single repump laser addressing the 3 P 2 → 3 D 2 transition at 496.93 nm may be used [15,16]. Until now the generation of light at this wavelength relied on second harmonic generation (SHG) from an infrared laser due to the lack of laser diodes directly operating in this range.…”