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Physical Review Applied

Two-Color Grating Magneto-Optical Trap for Narrow-Line Laser Cooling

Saskia Bondza, Christian Lisdat, Stefanie Kroker, Tobias Leopold

Published Apr 1, 2022• 25 citations
Publisher

Abstract

We demonstrate the two-color cooling and trapping of alkaline-earth atoms in a grating magneto-optical trap (GMOT). The trap is formed by a single incident laser beam together with four secondary beams that are generated via diffraction from a nanostructured wafer. A grating structure for a GMOT operating with strontium atoms is optimized and fabricated. We trap ${10}^{6}{\phantom{\rule{0.2em}{0ex}}}^{88}\mathrm{Sr}$ atoms on the ${}^{1}{S}_{0}{\ensuremath{\rightarrow}}^{1}{P}_{1}$ transition at $461\phantom{\rule{0.2em}{0ex}}\mathrm{nm}$ and transfer 25% of these atoms to the second cooling stage on the narrower ${}^{1}{S}_{0}{\ensuremath{\rightarrow}}^{3}{P}_{1}$ intercombination transition at $689\phantom{\rule{0.2em}{0ex}}\mathrm{nm}$, preparing a sample of $2.5\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms at $5\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{K}$. These results demonstrate the applicability of the GMOT technology in conjunction with two widely differing wavelengths and enable the continued miniaturization of alkaline-earth-based quantum technologies like optical atomic clocks.

DOI
10.1103/physrevapplied.17.044002

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We demonstrate the two-color cooling and trapping of alkaline-earth atoms in a grating magneto-optical trap (GMOT). The trap is formed by a single incident laser beam together with four secondary beams that are generated via diffraction from a nanostructured wafer. A grating structure for a GMOT operating with strontium atoms is optimized and fabricated. We trap 10688Sr{10}^{6}{\phantom{\rule{0.2em}{0ex}}}^{88}\mathrm{Sr}10688Sr atoms on the 1S0\ensuremath→1P1{}^{1}{S}_{0}{\ensuremath{\rightarrow}}^{1}{P}_{1}1S0​\ensuremath→1P1​ transition at 461nm461\phantom{\rule{0.2em}{0ex}}\mathrm{nm}461nm and transfer 25% of these atoms to the second cooling stage on the narrower 1S0\ensuremath→3P1{}^{1}{S}_{0}{\ensuremath{\rightarrow}}^{3}{P}_{1}1S0​\ensuremath→3P1​ intercombination transition at 689nm689\phantom{\rule{0.2em}{0ex}}\mathrm{nm}689nm, preparing a sample of 2.5\ifmmode×\else\texttimes\fi1052.5\ifmmode\times\else\texttimes\fi{}{10}^{5}2.5\ifmmode×\else\texttimes\fi105 atoms at 5\ensuremathμK5\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{K}5\ensuremathμK. These results demonstrate the applicability of the GMOT technology in conjunction with two widely differing wavelengths and enable the continued miniaturization of alkaline-earth-based quantum technologies like optical atomic clocks.
We demonstrate for the first time the two-color cooling and trapping of alkaline-earth atoms in a grating magneto-optical trap (gMOT). The trap is formed by a single incident laser beam together with four secondary beams that are generated via diffraction from a nanostructured wafer. A grating structure for a gMOT operating with strontium atoms is optimized and fabricated. We trap 10610^6106 88^{88}88Sr atoms on the 1^11S0_00​ →\rightarrow→ 1^11P1_11​ transition at 461  nm461\;\mathrm{nm}461nm and transfer 25  %25\;\%25% of these atoms to the second cooling stage on the narrower 1^11S0_00​ →\rightarrow→ 3^33P1_11​ intercombination transition at 689  nm689\;\mathrm{nm}689nm, preparing a sample of 2.5×1052.5\times 10^52.5×105 atoms at 5  μ5\;μ5μK. These results demonstrate for the first time the applicability of the gMOT technology in conjunction with two widely differing wavelengths and enable the continued miniaturization of alkaline-earth based quantum technologies like optical atomic clocks.
We demonstrate a compact magneto-optical trap (MOT) of alkaline-earth atoms using a nanofabricated diffraction grating chip. A single input laser beam, resonant with the broad 1S0 → 1P1 transition of strontium, forms the MOT in combination with three diffracted beams from the grating chip and a magnetic field produced by permanent magnets. A differential pumping tube limits the effect of the heated, effusive source on the background pressure in the trapping region. The system has a total volume of around 2.4 l. With our setup, we have trapped up to 5 × 106 88Sr atoms at a temperature of ∼6 mK, and with a trap lifetime of ∼1 s. Our results will aid the effort to miniaturize quantum technologies based on alkaline-earth atoms.
We report laser cooling and trapping of ytterbium atoms in a two-color magneto-optical trap (MOT). Benefited from both the broad singlet transition (1S0→1P1^1\text{S}_0\rightarrow {}^1\text{P}_11S0​→1P1​) and the narrow intercombination transition (1S0→3P1^1\text{S}_0\rightarrow {}^3\text{P}_11S0​→3P1​) of ytterbium atoms, the two-color MOT enables rapid loading and efficient cooling. We systematically investigate the shielding effect of the intercombination transition by examining the atom loading and loss rates of single-color and two-color MOTs. Our findings are general and can be extended to other alkaline earth(-like) atoms.
We present a two-dimensional grating magneto-optical trap (2D gMOT) for strontium, which produces a slow atomic beam in a compact form factor. The strontium 2D gMOT, using permanent magnets with an atomic dispenser, cools and traps atoms along two dimensions in the diffraction plane of a grating chip using the 1 S 0 → 1 P 1 (blue) transition. The system is configured in such a way that the atoms emitted from the dispenser source do not degrade the diffraction efficiency of the grating for long-term stable use. The performance of the 2D gMOT is analyzed with plug and probe beams, where the atomic source achieves a flux of 2.1 × 10 8 atoms/s and mean velocity of 6.4 m/s for an input laser power of 75 mW. The velocity measurement allows for the precise characterization of atom-photon scattering properties, showing that the compact 2D gMOT is suitable for portable quantum devices such as atomic clocks, quantum sensors, and precision spectroscopy.
We demonstrate a two-dimensional (2D) grating magneto-optical trap (GMOT) with a single input cooling laser beam and a planar diffraction grating using 87Rb^{87}\mathrm{Rb}87Rb. This configuration increases experimental access when compared with a traditional 2D magneto-optical trap (MOT). As described in the paper, the output flux is several hundred million rubidium atoms/s at a mean velocity of 16.5(9) m/s and a velocity distribution of 4(3) m/s standard deviation. We use the atomic beam from the 2D GMOT to demonstrate loading of a three-dimensional (3D) GMOT with $2.46(7)\ifmmode\times\else\texttimes\fi{}{10}^{8}$ atoms. Methods to improve output flux are discussed.
We present an experimental scheme for producing ultracold ytterbium atoms in a compact dual-chamber setup. A dispenser-loaded two-dimensional magneto-optical trap (MOT) using permanent magnets and operating on the broad ${}^{1}{S}_{0}\ensuremath{\rightarrow}{}^{1}{P}_{1}$ singlet transition delivers over 107{10}^{7}107 atoms per second through a differential pumping stage into a three-dimensional MOT. The two-color three-dimensional MOT uses the broad singlet transition to accumulate $\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}{10}^{7}$ atoms of 174Yb{}^{174}\mathrm{Yb}174Yb within 2.5 s and subsequently the narrow ${}^{1}{S}_{0}\ensuremath{\rightarrow}{}^{3}{P}_{1}$ intercombination line to cool the atomic cloud to below 10 \textmu{}K. We report optimized parameters for each stage of the atom collection sequence, achieving high transfer efficiency. We find that shelving into the triplet state during the broad-transition MOT almost doubles the number of trapped atoms.