Characterization of an ultra-stable optical cavity

We report the main characteristics and performances of the first – to our knowledge – prototype of an ultra-stable cavity designed and produced by industry with the aim of space missions. The cavity is a 100 mm long cylinder rigidly held at its midplane by an engineered mechanical interface providing an efficient decoupling from thermal and vibration perturbations. The spacer is made from Ultra-Low Expansion (ULE) glass and mirrors substrate from fused silica to reduce the thermal noise limit to 4x10. Finite element modeling was performed in order to minimize thermal and vibration sensitivities while getting a high fundamental resonance frequency. The system was designed to be transportable, acceleration tolerant (up to several g) and temperature range compliant [-33°C; +73°C]. The axial vibration sensitivity was evaluated at 4x10 /(ms), while the transverse one is < 1x10 /(ms). The fractional frequency instability is < 1x10 from 0.1 to few seconds and reaches 5-6x10 at 1s.