Design Of An Optical Reference Cavity With Flexible Thermal Expansion Tuning Properties

An ultra-stable optical cavity is designed as the frequency reference of a clock laser for an Al + optical clock by finite element analysis (FEA). The cavity has a structure with fused silica (FS) mirrors contacted to FS rings and re-entrant inside the ULE spacer. This design yields a low thermal noise limit and a flexible tuning range of the total coefficient of thermal expansion (CTE) which is suitable for applications with ULE materials that have various zero-crossing temperatures of CTE from 5 degrees C to 35 degrees C, and for applications for cavities with various dimensions and configurations.