A spaceborne mounting method for fixing a 100 × 100 × 100 mm cubic Fabry–Pérot (FP) cavity is presented. The method constrains the FP cavity in eight directions with a titanium bracket, PEEK gaskets, and vacuum glue. Three criteria were proposed for judging whether the FP cavity is offset or not during aerospace vibration tests. Results indicate that the proposed method is a reliable, robust, and stable way to fix a cubic FP cavity in ultra-stable lasers (USLs). This approach paves the way for the use of USLs in space.

A domestic space-borne transportable FP cavity is designed. The cavity length is 100 mm with the shape of a cube. Spacer is made of ultra-low expansion glass. This cavity is four-point mounting and heat insulated from external environmental fluctuation. To judge the performance of this cavity, an ultra-stable laser based on this cavity was constructed, the frequency noise of which is below 30Hz/ √ Hz, which can fulfill the requirements of the Taiji-2 mission.