Can TCOs Transform Cavity-QED?

TL;DR

This paper demonstrates that a ZnO-based transparent conductive oxide significantly reduces optical loss in high-finesse micro-resonators, enabling new possibilities in cavity-QED systems.

Contribution

It introduces a ZnO TCO with ultra-low optical absorption, achieving high finesse in optical cavities, surpassing previous materials like ITO.

Findings

22,000 finesse at 1650 nm with ZnO coating

5000 times lower optical loss than ITO

0.01 Ω·cm surface resistivity at DC

Abstract

Transparent conductive oxides (TCO) enable confinement of charge-sensitive ions and Rydberg atoms proximal to dielectric structures including waveguides and photon detectors. However, optical loss precludes the use of TCOs within high-finesse optical micro-resonators. Here we characterize a ZnO-based TCO that markedly reduces optical absorption. At 1650\text{ nm} we observe a 22,000 finesse in a Fabry-P\'erot optical cavity coated with a 30\text{ nm} ZnO layer. This is a 5000 times reduction relative to indium tin oxide (ITO) at this wavelength. The same ZnO film exhibits 0.01\text{ \ensuremath{\Omega}\ensuremath{\cdot}cm} surface resistivity at DC. We anticipate a step change in cavity-QED systems incorporating ultra-low loss TCOs like ZnO.