Effect of heat treatment on mechanical dissipation in Ta$_2$O$_5$ coatings

TL;DR

This study investigates how post-deposition heat treatment affects the temperature-dependent mechanical dissipation in Ta₂O₅ coatings, revealing that heat treatment significantly influences coating thermal noise relevant to precision measurement systems.

Contribution

It provides new insights into the relationship between heat treatment conditions and mechanical dissipation in Ta₂O₅ coatings, highlighting the impact on thermal noise.

Findings

Dissipation temperature dependence varies with heat treatment temperature.

Three dissipation peaks identified at different heat treatment conditions.

Higher heat treatment temperatures increase mechanical loss below 200 K.

Abstract

Thermal noise arising from mechanical dissipation in dielectric reflective coatings is expected to critically limit the sensitivity of precision measurement systems such as high-resolution optical spectroscopy, optical frequency standards and future generations of interferometric gravitational wave detectors. We present measurements of the effect of post-deposition heat treatment on the temperature dependence of the mechanical dissipation in ion-beam sputtered tantalum pentoxide between 11\,K and 300\,K. We find the temperature dependence of the dissipation is strongly dependent on the temperature at which the heat treatment was carried out, and we have identified three dissipation peaks occurring at different heat treatment temperatures. At temperatures below 200\,K, the magnitude of the loss was found to increase with higher heat treatment temperatures, indicating that heat treatment is a significant factor in determining the level of coating thermal noise.