  The sensitivity of ground-based gravitational wave (GW) detectors will be
improved in the future via the injection of frequency-dependent squeezed
vacuum. The achievable improvement is ultimately limited by losses of the
interferometer electromagnetic field that carries the GW signal. The analysis
and reduction of optical loss in the GW signal chain will be critical for
optimal squeezed light-enhanced interferometry. In this work we analyze a
strategy for reducing output-side losses due to spatial mode mismatch between
optical cavities with the use of adaptive optics. Our goal is not to design a
detector from the top down, but rather to minimize losses within the current
design. Accordingly, we consider actuation on optics already present and one
transmissive optic to be added between the signal recycling mirror and the
output mode cleaner. The results of our calculation show that adaptive
mode-matching with the current Advanced LIGO design is a suitable strategy for
loss reduction that provides less than 2% mean output mode-matching loss. The
range of actuation required is +47 uD on SR3, +140 mD on OM1 and OM2, +50 mD on
the SRM substrate, and -50 mD on the added new transmissive optic. These
requirements are within the demonstrated ranges of real actuators in similar or
identical configurations to the proposed implementation. We also present a
novel technique that graphically illustrates the matching of interferometer
modes and allows for a quantitative comparison of different combinations of
actuators.
