Alignment and Optimisation of Optical Tweezers on Trapped Ions

TL;DR

This paper develops a method to align optical tweezers on trapped ions, characterizes their properties, and demonstrates scalability for multiple ions using a spatial light modulator.

Contribution

It introduces a routine for precise alignment and characterization of optical tweezers on ions, including minimal waist measurement and effects analysis, enabling scalable multi-ion trapping.

Findings

Achieved a tweezer waist of 2.3 μm matching theoretical limits.

Characterized the spatial dependence of Rabi frequency suppression.

Demonstrated scalability to multiple ions with a spatial light modulator.

Abstract

This paper presents a routine to align an optical tweezer on a single trapped ion and use the ion as a probe to characterize the tweezer. We find a smallest tweezer waist of $2.3(2)\,\mu$m, which is in agreement with the theoretical minimal attainable waist of $2.5(2)\,\mu$m in our setup. We characterize the spatial dependence of the tweezer Rabi frequency which is suppressed by a factor of 19(3) in the immediate surrounding of the ion. We investigate the effects of optical forces and coherent population trapping on the ion. Finally, we show that the challenges posed by these forces can be overcome, and that the number of tweezers can be easily scaled up to reach several ions by using a spatial light modulator.