Stable double-resonance optical spring in laser gravitational-wave   detectors
  We analyze the optical spring characteristics of a double pumped Fabry-Perot cavity. A double-resonance optical spring occurs when the optical spring frequency and the detuning frequency of the cavity coincide. We formulate a simple criterion for the stability of an optical spring and apply it to the double resonance regime. Double resonance configurations are very promising for future gravitational wave detectors as they allow us to surpass the Standard Quantum Limit. We show that stable double resonance can be demonstrated in middle scale prototype interferometers such as the Glasgow 10m-Prototype, Gingin High Optical Power Test Facility or the AEI 10m Prototype Interferometer before being implemented in future gravitational wave detectors. 
Andrey Rakhubovsky, Stefan Hild and Sergey Vyatchanin
gr-qc