Efficient direct loading of the green MOT of Yb with low green laser power

TL;DR

This paper demonstrates a low-power green magneto-optical trap (MOT) for ytterbium atoms by superimposing green and blue lasers, achieving efficient loading with minimal laser power and novel dual MOT configurations.

Contribution

It introduces a method for directly loading Yb atoms into a green MOT using limited green laser power and a shifted dual MOT setup, enhancing efficiency without losing blue laser power.

Findings

Loaded up to 3×10^8 atoms in 1 second

Characterized effects of magnetic field, laser power, and detuning

Achieved green MOT loading with only 10 mW green laser power

Abstract

We report the direct loading of Yb atoms in the magneto-optical trap (MOT) using the intercombination narrow optical transition 6s$^2$ $^1$S$_0$ $\rightarrow$ 6s6p $^3$P$_1$ at 556 nm (green), known as green MOT with limited power of green laser, 10 mW. Direct loading of the green MOT is achieved by superimposing the green laser beam, inside a hollow core of the laser beam driving the broad 6s$^2$ $^1$S$_0$ $\rightarrow$ 6s6p $^1$P$_1$, transition (blue) at 399 nm. We load up to 3$\times10^8$ in $1$ s. We characterize the green MOT loading with various experimental parameters such as magnetic field gradient, power of the green laser and blue MOT laser, and detuning of the green laser. We have also loaded the green MOT using center-shifted dual MOT configuration. In this configuration, the overlap region of the three counter-propagating blue laser beams is shifted towards Zeeman slower, where the magnetic field is non-zero. The atoms are first pre-cooled and partially trapped in blue MOT. These atoms enter the green MOT region and are trapped. In this method, we do not lose power (unlike in core-shell MOT) of the blue MOT laser because of masking the central portion. However, we load only 10$^7$ atoms, which has one order of magnitude fewer atoms than in the core-shell MOT.