Red- and blue-detuned magneto-optical trapping with liquid crystal variable retarders

TL;DR

This paper demonstrates a simplified, cost-effective method for switching between red- and blue-detuned magneto-optical traps for rubidium atoms using liquid crystal variable retarders, achieving sub-Doppler temperatures and increased phase space density.

Contribution

Introducing a fast, compact polarization control method with liquid crystal variable retarders for efficient red- and blue-detuned MOTs in rubidium atoms.

Findings

Achieved blue-detuned type-II MOT with 44.5 μK temperature

Increased phase space density by over two orders of magnitude

Setup easily adaptable to other rubidium systems

Abstract

We exploit red- and blue-detuned magneto optical trapping (MOT) of $^{87}$Rb benefitting from a simplified setup based on liquid crystal variable retarders (LCVR). To maintain the trapping forces when switching from a red- to a blue-detuned MOT, the circularity of the cooling beams needs to be reversed. LCVRs allow fast polarization control and represent compact, simple and cost-efficient components which can easily be implemented in existing laser systems. This way, we achieve a blue-detuned type-II MOT for $^{87}$Rb atoms with sub-Doppler temperatures of 44.5 $\mu$K. The phase space density is increased by more than two orders of magnitude compared to the standard red-detuned type-I MOT. The setup can readily be transferred to any other system working with $^{87}$Rb.