Optical rigidity in a stable double-resonance regime

The properties of the optical rigidity created by double pumping in an interferometric gravitational-wave antenna are investigated. The double-resonance regime takes place when two eigenfrequencies of the system coincide with each other. A simple criterion of the stability of the optical rigidity is proposed and is applied to calculations of the double-resonance regime. The schemes of gravitational-wave antennas using such a regime are very promising because they allow overcoming the Standard Quantum Limit. We show that a stable double-resonance regime can be realized in laboratory prototypes before its implementation in full-scale gravitational-wave detectors.