Applied Physics Express

Continuous outcoupling of ultracold strontium atoms combining three different traps

Ryoto Takeuchi, Hayaki Chiba, 翔一岡場, Masao Takamoto, Shigenori Tsuji, Hidetoshi Katori

Published Apr 1, 2023• 16 citations

Abstract

Abstract We have demonstrated the continuous outcoupling of ultracold 88 Sr atoms using a moving optical lattice. While Sr atoms are Zeeman-slowed and magneto-optically trapped on the 1 S 0 – 1 P 1 transition, the atoms relaxed to the 5s5p 3 P 2 metastable state are magnetically trapped and Doppler cooled on the 5s5p 3 P 2 –5s4d 3 D 3 transition at 2.92 μ m. By optically pumping the atoms to the 5s5p 3 P 0 state, we outcouple the atoms by a moving optical lattice. Such a continuous atomic source enables superradiant lasers and the zero-dead-time operation of atom interferometers and optical lattice clocks.

DOI: 10.35848/1882-0786/accb3c

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Applied Physics Express

Continuous outcoupling of ultracold strontium atoms combining three different traps

Ryoto Takeuchi, Hayaki Chiba, 翔一岡場, Masao Takamoto, Shigenori Tsuji, Hidetoshi Katori

Published Apr 1, 2023• 16 citations

Publisher

Abstract

DOI: 10.35848/1882-0786/accb3c

Related papers

Narrow-line-mediated Sisyphus cooling in the P 2 3 metastable state of strontium

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We describe repumping and spectroscopy of laser-cooled strontium (Sr) atoms using the (5s5p) 3 P 2 –(5s4d) 3 D 2 transition. Atom number in a magneto-optical trap is enhanced by driving this transition because Sr atoms that have decayed into the (5s5p) 3 P 2 dark state are repumped back into the (5s 2 ) 1 S 0 ground state. Spectroscopy of 84 Sr, 86 Sr, 87 Sr and 88 Sr improves the value of the (5s5p) 3 P 2 –(5s4d) 3 D 2 transition frequency and determines the isotope shifts for the transition accurately enough to guide laser-cooling experiments with less abundant isotopes.We describe repumping and spectroscopy of laser-cooled strontium (Sr) atoms using the (5s5p) 3 P 2 –(5s4d) 3 D 2 transition. Atom number in a magneto-optical trap is enhanced by driving this transition because Sr atoms that have decayed into the (5s5p) 3 P 2 dark state are repumped back into the (5s 2 ) 1 S 0 ground state. Spectroscopy of 84 Sr, 86 Sr, 87 Sr and 88 Sr improves the value of the (5s5p) 3 P 2 –(5s4d) 3 D 2 transition frequency and determines the isotope shifts for the transition accurately enough to guide laser-cooling experiments with less abundant isotopes.

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Rodrigo González Escudero, Chun-Chia Chen, Shayne Bennetts +2 more

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Experimental research on loading strontium bosons into the optical lattice operating at the “magic” wavelength

Tian Xiao, Wang Ye-Bing, Lu Ben-Quan +7 more

The optical lattice clock with neutral atoms occupies an outstanding position in the research field of atomic clocks, demonstrating the great potential of its performance (like the uncertainty and the stability). At present, the optical lattice clock has realized a 10-18 level of its uncertainty. In this paper, we present the realization of loading bosonic atoms 88Sr (strontium, alkaline-earth metals) into a one-dimensional (1D) optical lattice in our laboratory. The optical lattice where the atoms are trapped can make the energy level shift, called Stark shift. But there is the special optical lattice operating at the “magic” wavelength for clock transitions (5s2) 1S0-(5s5p) 3P0, which can make the same Stark light-shift for both of them, indicating a zero light-shift relative to the clock. In our experiment, Sr atoms are cooled in a two-stage cooling and its temperature can be as low as 2 μK. Then these cold atoms are confined in the Lamb-Dicke region by the lattice laser output from an amplified diode laser operating at the “magic” wavelength, 813 nm. Experimentally, it is straightforward to provide 850 mW of lattice power focused to a 38 μm beam radius. After the cold atoms have trapped in the optical lattice, the lifetime of atoms in 1D optical lattice is measured to be 270 ms. The temperature and the number are about 3.5 μK and 1.2×105 respectively. Besides, effects of the power of the lattice laser on both the number and temperature are analyzed. The number changes linearly with the laser power, while there is no obvious influence on the temperature by the power. This original and special approach for atoms trapped in the optical lattice can provide a long interrogation time for probing the clock transition. Furthermore, it may be the foundation for developing our optical lattice clock of strontium atoms.The optical lattice clock with neutral atoms occupies an outstanding position in the research field of atomic clocks, demonstrating the great potential of its performance (like the uncertainty and the stability). At present, the optical lattice clock has realized a 10-18 level of its uncertainty. In this paper, we present the realization of loading bosonic atoms 88Sr (strontium, alkaline-earth metals) into a one-dimensional (1D) optical lattice in our laboratory. The optical lattice where the atoms are trapped can make the energy level shift, called Stark shift. But there is the special optical lattice operating at the “magic” wavelength for clock transitions (5s2) 1S0-(5s5p) 3P0, which can make the same Stark light-shift for both of them, indicating a zero light-shift relative to the clock. In our experiment, Sr atoms are cooled in a two-stage cooling and its temperature can be as low as 2 μK. Then these cold atoms are confined in the Lamb-Dicke region by the lattice laser output from an amplified diode laser operating at the “magic” wavelength, 813 nm. Experimentally, it is straightforward to provide 850 mW of lattice power focused to a 38 μm beam radius. After the cold atoms have trapped in the optical lattice, the lifetime of atoms in 1D optical lattice is measured to be 270 ms. The temperature and the number are about 3.5 μK and 1.2×105 respectively. Besides, effects of the power of the lattice laser on both the number and temperature are analyzed. The number changes linearly with the laser power, while there is no obvious influence on the temperature by the power. This original and special approach for atoms trapped in the optical lattice can provide a long interrogation time for probing the clock transition. Furthermore, it may be the foundation for developing our optical lattice clock of strontium atoms.

Acta Physica SinicaJan 1, 20150 citations

Narrow-line-mediated Sisyphus cooling in the

^{3}\mathrm{P}_{2}

metastable state of strontium

We demonstrate narrow-line-mediated Sisyphus cooling of magnetically trapped strontium (Sr) in the

5s5p\,^{3}\textrm{P}_{2}

state. A 641 nm standing-wave, blue-detuned from the

5s4d\,^{3}\textrm{D}_{3}

\,\rightarrow

\,5p4d\,^{3}\textrm{F}_{4}

transition, creates a dissipative optical lattice in the

^{3}\textrm{D}_{3}

state. By combining Doppler cooling and Sisyphus cooling on the

5s5p\,^{3}\textrm{P}_{2}

\,\rightarrow

5s4d\,^{3}\textrm{D}_{3}

transition at 2.92

μ

m, we observed efficient cooling of magnetically trapped atoms. By optically pumping the atoms to the

5s5p\,^{3}\textrm{P}_{0}

state, we facilitate continuous outcoupling via a moving optical lattice with two fold improvement in atom number. Our scheme applies to next-generation quantum sensors using continuous ultracold atomic beams.

Using orthogonally crossed moving lattices, we demonstrate the continuous transport of

{}^{88}\mathrm{Sr}

atoms in the long-lived metastable

{}^{3}{P}_{0}

and

{}^{3}{P}_{2}

states to a region free from scattered laser-cooling light, while two-stage cooling on the

{}^{1}{S}_{0}--{}^{1}{P}_{1}

and

{}^{3}{P}_{2}--{}^{3}{D}_{3}

transitions is being conducted. The transfer efficiency between the crossed lattices was close to unity when laser cooling was applied in the crossed region. For a clock laser propagating along the lattice axis, such a lattice-trapped atomic beam enables continuous interrogation of the clock transition free from the Doppler effect arising from the thermal motion of atoms.

A steady-state magneto-optical trap (MOT) of fermionic strontium atoms operating on the

7.5\text{-kHz}

-wide $^{1}S_{0}\text{\ensuremath{-}}^{3}P_{1}$ transition is demonstrated. This MOT contains $8.4\ifmmode\times\else\texttimes\fi{}{10}^{7}\phantom{\rule{0.16em}{0ex}}\mathrm{atoms}$, a loading rate of $1.3\ifmmode\times\else\texttimes\fi{}{10}^{7}\phantom{\rule{0.16em}{0ex}}\mathrm{atoms}/\mathrm{s}$, and an average temperature of $12\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{K}$. These parameters make it well suited to serve as a source of atoms for continuous-wave superradiant lasers operating on strontium's mHz-wide clock transition. Such lasers have only been demonstrated using pulsed Sr sources, limiting their range of applications. Our MOT makes an important step toward continuous operation of these devices, paving the way for continuous active optical clocks.