The ``optical springs'' regime of the signal-recycled configuration of laser interferometric gravitational-wave detectors is analyzed taking in account optical losses in the interferometer arm cavities. This regime allows to obtain sensitivity better than the Standard Quantum Limits both for a free test mass and for a conventional harmonic oscillator. The optical losses restrict the gain in sensitivity and achievable signal-to-noise ratio. Nevertheless, for parameters values planned for the Advanced LIGO gravitational-wave detector, this restriction is insignificant.
@article{arxiv.gr-qc/0511008,
title = {Sub-SQL Sensitivity via Optical Rigidity in Advanced LIGO Interferometer with Optical Losses},
author = {F. Ya. Khalili and V. I. Lazebny and S. P. Vyatchanin},
journal= {arXiv preprint arXiv:gr-qc/0511008},
year = {2009}
}