Blue-detuned magneto-optical trap

TL;DR

This paper introduces a blue-detuned magneto-optical trap for rubidium atoms that achieves higher density and lower temperature than traditional MOTs, enhancing its potential for molecular trapping applications.

Contribution

The study demonstrates a novel blue-detuned MOT with superior phase-space density and reduced atom loss, especially beneficial for molecular MOTs relying on type-II transitions.

Findings

Achieved density >10^{11}cm^{-3} with temperatures below 30μK.

Phase-space density exceeds that of normal and red-detuned type-II MOTs.

Measured atom loss rate of approximately 1.8×10^{-10}cm^{3}s^{-1}.

Abstract

We present the properties and advantages of a new magneto-optical trap (MOT) where blue-detuned light drives `type-II' transitions that have dark ground states. Using $^{87}$Rb, we reach a radiation-pressure-limited density exceeding $10^{11}$cm$^{-3}$ and a temperature below 30$\mu$K. The phase-space density is higher than in normal atomic MOTs, and a million times higher than comparable red-detuned type-II MOTs, making it particularly attractive for molecular MOTs which rely on type-II transitions. The loss of atoms from the trap is dominated by ultracold collisions between Rb atoms. For typical trapping conditions, we measure a loss rate of $1.8(4)\times10^{-10}$cm$^{3}$s$^{-1}$.