Atoms loading and cooling for an optical cavity assisted by Λ-enhanced gray-molasses cooling process
Authors: Liu Yan-Xin , Wang Zhi-Hui , Guan Shi-Jun , Wang Qin-Xia , Zhang Peng-Fei , Li Gang , Zhang Tian-Cai ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China,   Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
Published: April 2024

Λ-enhanced gray molasses cooling (Λ-GMC) technique has been widely used in experiments to prepare cold atomic samples below the sub-Doppler temperature limit. To meet the experimental requirements of cavity quantum electrodynamics systems, we design and construct a wide-range, fast-tuning laser system by integrating tapered amplifiers, fiber phase modulators, etalon, injection locking amplification techniques etc. This laser system achieves a maximum tuning range of 600 MHz and a frequency tuning speed of 5 ns. Based on this laser system, loading atom in a crossed dipole trap assisted by cesium D2 line Λ-GMC cooling in the center of the optical microcavity is studied, and various factors affecting the atom loading are mainly as follows: laser duration <inline-formula><tex-math id="M4">\begin{document}$\tau $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M4.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M4.png"/></alternatives></inline-formula>, three-dimensional magnetic field <inline-formula><tex-math id="M5">\begin{document}$ \left( {{B_x}, {B_y}, {B_z}} \right) $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M5.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M5.png"/></alternatives></inline-formula>, single-photon detuning <inline-formula><tex-math id="M6">\begin{document}$\varDelta $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M6.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M6.png"/></alternatives></inline-formula>, two-photon detuning <inline-formula><tex-math id="M7">\begin{document}$\delta $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M7.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M7.png"/></alternatives></inline-formula>, ratio of cooling beam power to repumping beam power <inline-formula><tex-math id="M8">\begin{document}${I_{{\text{cool}}}}/{I_{{\text{rep}}}}$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M8.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M8.png"/></alternatives></inline-formula>, and cooling beam power <inline-formula><tex-math id="M9">\begin{document}${I_{{\text{cooling}}}}$\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M9.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M9.png"/></alternatives></inline-formula>. The optimal parameters in this system are follows: <inline-formula><tex-math id="M10">\begin{document}$ \tau = 7{\text{ ms}},\; \delta = 0.2{\text{ MHz}},\; \varDelta = 5\varGamma, \;{I_{{\text{cool}}}}/{I_{{\text{rep}}}} = 3, {\text{ and }} {I_{{\text{cool}}}} = 1.2{I_{{\text{sat}}}}. $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M10.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M10.png"/></alternatives></inline-formula> Comparing with traditional PGC-assisted loading, the number of atoms is increased about 4 times, and the atomic temperature decreases from <inline-formula><tex-math id="M11">\begin{document}$ 25{\text{ μK}} $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M11.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M11.png"/></alternatives></inline-formula> to <inline-formula><tex-math id="M12">\begin{document}$ 8{\text{ μK}} $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M12.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240182_M12.png"/></alternatives></inline-formula>. This experiment provides important insights for preparing ultracold atomic samples and capturing single atom arrays.