We report on the demonstration of a light-matter interface coupling light to a single 174Yb+ ion in free space. The interface is realized through a parabolic mirror partially surrounding the ion. It transforms a Laguerre-Gaussian beam into a linear dipole wave converging at the mirror's focus. By measuring the non-linear response of the atomic transition we deduce the power required for reaching an upper-level population of 1/4 to be 692±20pW at half linewidth detuning from the atomic resonance. Performing this measurement while scanning the ion through the focus provides a map of the focal intensity distribution. From the measured power we infer a coupling efficiency of 7.2±0.2% on the linear dipole transition when illuminating from half solid angle, being among the best coupling efficiencies reported for a single atom in free space.
@article{arxiv.1311.1982,
title = {Efficient saturation of an ion in free space},
author = {Martin Fischer and Marianne Bader and Robert Maiwald and Andrea Golla and Markus Sondermann and Gerd Leuchs},
journal= {arXiv preprint arXiv:1311.1982},
year = {2015}
}