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Characterization of laser cooling in microgravity via long-term operations in TianGong-2 space lab

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National Science Review 2023年第4期10卷 69-75页

作者： De-Sheng Lü Wei Ren Yuan Sun Tang Li Qiu-Zhi Qu Bin Wang Lin Li Jian-Bo Zhao Xin Zhao Jing-Wei Ji Mei-Feng Ye Jing-Feng Xiang Wei-Biao Chen Yu-Zhu Wang Liang Liu CAS Key Laboratory of Quantum Optics and Center of Cold Atom Physics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Aerospace laser Engineering Department Shanghai Institute of Optics and Fine MechanicsChinese Academy of Sciences

The invention of laser cooling has fundamentally influenced the research frontier of atomic physics and quantum physics, and recently an intense focus has been on the studies of cold atom physics in microgravity environments. Herein, we report the results of our laser cooling experiment in Tian Gong-2 space lab, which operated for 34 consecutive months in orbit. Over such an extended operation time, the quality of laser cooling did not experience any significant decline, while the properties of laser cooling in orbital microgravity were systematically studied. In particular, we demonstrate magneto-optical trapping and polarization-gradient cooling in orbit and carefully examine their performances. A comparison of the in-orbit and on-ground results indicates that a higher cooling efficiency exists in microgravity, including a smaller loss rate during the trapping and cooling process and lower ultimate temperature of laser-cooled atoms. Our progress has laid the technical foundations for future applications of cold atoms in space missions with operation times of the order of years.

关键词： laser cooling polarization-gradient cooling orbital microgravity space lab

laser cooling of CH molecule: Insights from ab initio study

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Chinese Physics B 2018年第10期27卷 276-282页

作者：崔洁徐建刚祁建霞窦戈张云光 School of Science Xi'an University of Posts and Telecommunications

The feasibility of laser cooling a CH molecule is investigated theoretically by employing the ab initio method. The potential energy curves for the five ∧-S states and eight Ω states of CH are determined by the multi-reference configuration interaction with the Davidson corrections（MRCI＋Q） level of theory. The results agree well with the available experimental data and other theoretical values. Also, the permanent dipole moments and transition dipole moments of the CH molecule are calculated at the multi-reference configuration interaction（MRCI） level. We find highly diagonally distributed FranckCondon factors（f00 = 0.9950 and 0.9998） and branching ratios（R00 = 0.983 and 0.993） for the A^2△→ X2Π and C^2∑^＋→X^2Π transitions. Moreover, the values of suitable radiative lifetime τ of the A2 A and C^2∑^＋ states are evaluated to be9.64×10^-7 s and 2.02×10^-7 s, respectively, for rapid laser cooling. A scheme for laser cooling the CH molecule is designed. In the proposed cooling scheme, three wavelengths for A^2△→X^2Π and C^2∑^＋→X^2Π transitions are used, and the main pump lasers are λ00=430.86 nm and 313.45 nm, respectively. The feasibility of laser cooling the CH molecules is demonstrated for each of these schemes, and this study offers a theoretical basis for experimental research into preparation of cold CH molecules.

关键词： spectroscopic constants transition diople moments Franck-Condon factors laser cooling

BaF radical： A promising candidate for laser cooling and magneto-optical trapping

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Chinese Physics B 2017年第3期26卷 321-329页

作者：许亮魏斌夏勇邓联忠印建平 State Key Laboratory of Precision Spectroscopy School of Physics and Materials Science East China Normal University Shanghai 200062 China

Recently, there have been great interest and advancement in the field of laser cooling and magneto-optical trapping of molecules. The rich internal structure of molecules naturally lends themselves to extensive and exciting applications. In this paper, the radical 138Ba19F, as a promising candidate for laser cooling and magneto-optical trapping, is discussed in detail.The highly diagonal Franck-Condon factors between theX2∑＋1/2and A2∏1/2states are first confirmed with three different methods. Afterwards, with the effective Hamiltonian approach and irreducible tensor theory, the hypertine structure of theX2∑＋1/2state is calculated accurately. A scheme for laser cooling is given clearly. Besides, the Zeeman effects of the upper （ A2∏1/2）andlower（X2∑＋1/2）levels are also studied, and their respective g factors are obtained under a weak magnetic field. Its large g factor of the upper stateA2∏1/2is advantageous for magneto-optical trapping. Finally, by studying Stark effect of BaFin theX2∑＋1/2, we investigate the dependence of the internal effective electric field on the applied electric field. It is suggested that such a laser-cooled BaF is also a promising candidate for precision measurement of electron electric dipole moment.

关键词： laser cooling magneto-optical trapping BaF radical

Cavity-enhanced laser cooling of solid-state materials in a standing-wave cavity

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Chinese Optics Letters 2008年第11期6卷 848-851页

作者：贾佑华钟标印建平 State Key Laboratory of Precision Spectroscopy.East China Normal University.Shanghai 200062

We propose a new method to cool the yb^3＋-doped ZBLANP glass in a standing-wave cavity. There are two advantages of this cavity-enhanced technique： the pumping power is greatly enhanced and the absorption of the cooling material is greatly increased. We introduce the basic principle of the cavity-enhanced laser cooling and discuss the cooling effect of a solid-state material in a cavity. From the theoretical study, it is found that the laser cooling effect is strongly dependent on the reflectivity of the cavity mirrors, the length of the solid material, the surface scattering of the material, and so on. Some optimal parameters for efficient laser cooling are obtained.

关键词： laser cooling lasers Mirrors Standing wave meters Ytterbium

Ab initio study on the electronic states and laser cooling of AlCl and AlBr

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Chinese Physics B 2016年第4期25卷 92-97页

作者：杨荣唐斌高涛 College of Materials Science and Engineering Chongqing Jiaotong University Institute of Atomic and Molecular Physics Sichuan University Institute of Finance & Trade Chongqing City Management College

We investigate whether A1C1 and A1Br are promising candidates for laser cooling. We report new ab initio calculations on the ground state X1E＋ and two low-lying states （A1H and a3H） of A1C1 and A1Br. The calculated spectroscopic constants show good agreement with available theoretical and experimental results. We also obtain the permanent dipole moments （PDMs） curve at multi-reference configuration interaction （MRCI） level of theory. The transition properties of A1H and a3H states are predicted, including the transition dipole moments （TDMs）, Franck-Condon factors （FCFs）, radiative times and radiative width. The calculated radiative lifetimes are of the order of a nanosecond, implying that they are sufficiently short for rapid laser cooling. Both A1C1 and A1Br have highly diagonally distributed FCFs which are crucial requirement for molecular laser cooling. The results demonstrate the feasibility of laser cooling A1C1 and A1Br, and we propose laser cooling schemes for A1C1 and A1Br.

关键词： A1C1 AIBr laser cooling

Engineering steady-state entanglement for two atoms held in separate cavities through laser cooling

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Chinese Physics B 2014年第4期23卷 109-112页

作者：沈利托陈荣鑫吴怀志杨贞标 Laboratory of Quantum Optics Department of Physics Fuzhou University

We propose a scheme to prepare the steady-state entanglement for two atoms, which are held in separate cavities that are coupled through a short optical fiber or optical resonator. The entangled steady-state with a high fidelity can be achieved even with a low cooperativity parameter, by making use of the driving laser fields. Such a cooling mechanism is based on a resonant laser pump of the unwanted ground states to the excited states, which finally decay to the desired steady-state.

关键词： laser cooling steady-state entanglement optical fiber

Exact results on cavity cooling in a system of a two-level atom and a cavity field

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Chinese Physics B 2010年第3期19卷 263-268页

作者：张玉青谭磊朱中华刘利伟 Institute of Theoretical Physics Lanzhou University

Using the algebraic dynamical method, this paper investigates the laser cooling of a moving two-level atom coupled to a cavity field. Analytical solutions of optical forces and the cooling temperatures are obtained. Considering Rb atoms as an example, it finds that the numerical results are relevant to the recent experimental laser cooling investigations.

关键词： laser cooling algebraic dynamical method optical forces cooling temperatures

Efficient loading of ultracold sodium atoms in an optical dipole trap from a high power fiber laser

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Chinese Physics B 2021年第3期30卷 237-241页

作者：徐静刘文良郑宁宣李玉清武寄洲李鹏付永明马杰肖连团贾锁堂 State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Laser SpectroscopyCollege of Physics and Electronics EngineeringShanxi UniversityTaiyuan 030006China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China

We report on a research of the loading of ultracold sodium atoms in an optical dipole trap,generated by two beams from a high power fiber laser.The effects of optical trap light power on atomic number,temperature and phase space density are experimentally investigated.A simple theory is proposed and it is in good accordance with the experimental results of the loaded atomic numbers.In a general estimation,an optimal value for each beam with a power of 9 W from the fiber laser is achieved.Our results provide a further understanding of the loading process of optical dipole trap and laid the foundation for generation of a sodium Bose–Einstein condensation with an optical dipole trap.

关键词： optical dipole trap laser cooling high power fiber laser

Microwave-mediated magneto-optical trap for polar molecules

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Chinese Physics B 2016年第5期25卷 159-163页

作者：谢笛舟卜文浩颜波 Department of Physics Zhejiang University

Realizing a molecular magneto-optical trap has been a dream for cold molecular physicists for a long time. However,due to the complex energy levels and the small effective Lande g-factor of the excited states, the traditional magneto-optical trap（MOT） scheme does not work very well for polar molecules. One way to overcome this problem is the switching MOT,which requires very fast switching of both the magnetic field and the laser polarizations. Switching laser polarizations is relatively easy, but fast switching of the magnetic field is experimentally challenging. Here we propose an alternative approach, the microwave-mediated MOT, which requires a slight change of the current experimental setup to solve the problem. We calculate the MOT force and compare it with the traditional MOT and the switching MOT scheme. The results show that we can operate a good MOT with this simple setup.

关键词： laser cooling cold molecules microwave-mediated magneto-optical trap（MOT）