High resolution spectroscopy of thulium atoms implanted in solid noble gas crystals

TL;DR

This study demonstrates that thulium atoms in solid argon and neon crystals exhibit narrow, well-resolved optical transitions at cryogenic temperatures, making them promising for quantum applications due to minimal inhomogeneous broadening.

Contribution

The paper reveals that thulium-doped noble gas crystals have exceptionally narrow optical lines, overcoming typical inhomogeneous broadening issues in solid-state quantum emitters.

Findings

Narrow ensemble linewidths as small as 0.6 GHz.

Splitting of the 1140 nm transition into multiple components.

Homogeneous broadening dominates over inhomogeneous effects.

Abstract

Optically active defects in solid-state systems have many applications in quantum information and sensing. However, unlike free atoms, which have fixed optical transition frequencies, the inhomogeneous broadening of the transitions in solid-state environments limit their use as identical scatterers for such applications. Here we show that crystals of argon and neon prepared in a closed-cycle cryostat doped with thulium atoms at cryogenic temperatures are an exception. High resolution absorption and emission spectroscopy show that the 1140 nm magnetic dipole transition is split into multiple components. The origin of this splitting is likely a combination of different classes of trapping sites, crystal field effects within each site, and hyperfine interactions. The individual lines have ensemble widths as small as 0.6 GHz, which temperature dependence and pump-probe spectroscopy indicate is likely a homogeneous effect, suggesting inhomogeneity is well below the GHz scale.