Optimal configurations of filter cavity in future gravitational-wave detectors

Sensitivity of future laser interferometric gravitational wave detectors can be improved using squeezed light with frequency-dependent squeeze angle and/or amplitude, which can be created using additional so-called filter cavities. Here we compare performances of several variants of this scheme, proposed during the last few years, assuming the case of a single relatively short (tens of meters) filter cavity suitable for implementation already during the life cycle of the second-generation detectors, like Advanced LIGO. Using numerical optimization, we show that the phase filtering scheme proposed by Kimble et al [H. J. Kimble, Yu. Levin, A. B. Matsko, K. S. Thorne, and S. P. Vyatchanin, Phys. Rev. D 65, 022002 (2001).] looks like the best candidate for this scenario.