Long-term temperature stabilized measurement of ultra-low expansion Fabry-Perot cavity

Abstract

The ultra low expansion cavities play a crucial role in laser stabilization, and they are essential in ion clocks. We present a method to measure absolute distance between mirrors of Fabry-Perot cavity (FPC) with a spacer from an ultra low expansion material and the changes of the distance caused by temperature variation with femtometer resolution. The FPC was placed into a temperature-stabilized vacuum stainless steel chamber.