Date of Award
Spring 2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Physics
First Advisor
Lamoreaux, Steve
Abstract
In recent years, there has been growing interest in methods for producing gases of ultracoldpolar molecules, driven by proposals to employ ultracold molecules in applications in ultracold chemistry, quantum information and quantum simulation, and precision measurements. There has been tremendous progress in producing ultracold polar molecules using pre-cooled and assembled alkali atoms, however, this faces limits in the molecule variety and interaction regimes that are accessible. Nonetheless, these techniques have successfully produced the first degenerate gases of polar molecules. Simultaneously, there has been a strong experimental and theoretical focus towards developing techniques to directly laser cool molecules which would enable accessing a diverse species of molecules in different interaction regimes. Here, we review recent advances in the laser cooling and trapping of Strontium Monofluoride (SrF). Building upon previous work, we utilize velocity-selective coherent population trapping to substantially lower the temperature and truly reach the ultracold regime. We then describe how we can use this technique to load a conservative optical dipole trap, the first step towards observing collisions between the molecules. We also describe how we can use the interplay of the differential energy shifts caused by trap light polarizations and the cooling light itself to greatly enhance the loading and reduce the temperature in the trap, heralding large trap densities even with a low molecules number. We detail a new molecule source based on ultracold chemistry that is able to produce a larger molecule flux and a greatly increased experiment lifetime. Next, we detail a new and novel trapping technique that incorporates blue-detuned light, which can achieve large compression of the molecule cloud while cooling it at the same time. Using this new technique, we are able to achieve two orders of magnitude larger density, a big boost for loading the optical dipole trap. We demonstrate that, owing to the small size of this cloud, we are able to load an order of magnitude more molecules than before. With this high density, we demonstrate a measurement of the two-body inelastic collision rate in the trap, the first such demonstration in a bulk gas of directly cooled molecules. We describe ongoing work to achieve quantum control of the molecules in the trap, and the current experimental push to prepare the molecules in the rovibrational ground state. We briefly describe the design of a next generation apparatus which will enable the future experiments towards a BEC. We then describe our efforts towards implementing microwave shielding to lower the inelastic loss rate while also enhancing the elastic collision rate. This is a prerequisite to implementing evaporative cooling, and we describe some estimates of how well this will work in our system. We outline a path to efficient evaporative cooling and find that a BEC is within reach.
Recommended Citation
Jorapur, Varun Rajeev, "Towards a Bose-Einstein Condensate of SrF molecules" (2024). Yale Graduate School of Arts and Sciences Dissertations. 1341.
https://elischolar.library.yale.edu/gsas_dissertations/1341
