Research on Laser Cooling and Optical Lattice of Strontium Atoms

Y. N. Martinez, Pascal G. Mickelson, Sarah Nagel +1 more

Zhanjun Fang

The Strontium cooling experiment realized to transfer atoms from the first stage broadband cooling to the second stage narrow line cooling.The temperature of the atoms after the second stage cooling is about 2μK.The lattice laser is on during the cooling process,so the atoms are loaded into the lattice when their temperature is low enough.cooled by narrow line cooling.

Chetan Vishwakarma

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.

Xin Na Tian, Y. B. Wang, H. Liu +6 more

At present the optical clock with accuracy and stability achieves to 10-18 level, which could be the next generation of time and frequency standard. This paper gives an introduction of the progress of researching on the optical lattice clock of Strontium atom in NTSC (National Time Service Center). We realize the (5s5s)1S0—(5s5p)1P1 cooling (blue MOT) and (5s5s)1S0—(5s5p)3P1 cooling (red MOT) in succession for the optical lattice clock, and loading these cold atoms in a lattice composed by a magic wave-length is studied. By using our narrow line-width diode laser and the fiber femtosecond optical frequency comb, we precisely measure the absolute frequencies of the inter-combination transitions (5s5s)1S0—(5s5p)3P1 of four isotopes of Strontium referenced to an H maser.

Benjamin Bloom, Sebastian Blatt, Travis Nicholson +5 more