Finite element analysis of zero-crossing temperature of long Fabry-Perot cavity

A Fabry-Perot (F-P) cavity with a low thermal noise limit 7.8×10-17 is investigated. The spacer aperture is composed of three holes, where a long and small hole in the middle, a shorter and larger hole on each side. The FS mirrors are placed in the larger holes of the spacer aperture, the FS rings are mounted on the end face of the spacer, and FS mirrors, aperture and FS rings are coaxial. It enables the cavity zero-crossing temperature easily tuning to above room temperature. In the meantime, with this design the machining error has little effect on the zero-crossing temperature of the cavity. In addition, it is convenient for manufacturing of long F-P cavity.