Blue-Detuned Magneto-Optical Trap of Polyatomic Molecules*

Over the last decade, laser cooling and magneto-optical traps (MOTs) have successfully been extended to molecules. Bulk gases of directly laser cooled molecules have, however, been limited to relatively low number and phase space densities. Higher densities are desired to realize several scientific goals, e.g., the realization of a quantum degenerate molecular gas from directly laser cooled molecules. A major obstacle towards higher densities has been the relatively high temperatures of molecular MOTs compared to their atomic counterparts. Recently, MOTs using blue-detuned light for the optical cycling transition, rather than the conventional choice of red-detuned cycling light, have been demonstrated with diatomic molecules [1-3]. Blue-detuned MOTs, which were first demonstrated with Rb atoms [4], provide gray molasses sub-Doppler cooling, resulting in lower temperatures and significantly higher densities compared to red-detuned molecular MOTs. Here we demonstrate a blue-detuned MOT for a polyatomic molecule, calcium monohydroxide (CaOH). CaOH molecules are captured from a red-detuned MOT and then loaded into the blue-detuned MOT, where rapid spatial compression is achieved from an initial cloud size of ~0.5 mm to ~0.06 mm, over ~5 ms. Numerical simulations show good agreement with our experimental results and provide qualitative comparisons between the blue-detuned CaOH MOT and blue-detuned MOTs demonstrated with diatomic molecules.

[1] J. J. Burau, P. Aggarwal, K. Mehling, and J. Ye, PRL 130, 193401 (2023)

[2] V. Jorapur, T. K. Langin, Q. Wang, G. Zheng, and D. DeMille, arXiv:2307.05347 (2023)

[3] S. J. Li, C. M. Holland, Y. Lu, and L. W. Cheuk, arXiv:2311.05447 (2023)

[4] K. N. Jarvis, J. A. Devlin, T. E. Wall, B. E. Sauer, and M. R. Tarbutt, PRL 120, 083201 (2018)