Research on the use of "squeezed light" in a complete LIGO detector has been underway on the enhanced LIGO 4km interferometer at Hanford (H1) . Recently, the squeezed light team has successfully demonstrated a nearly 1dB improvement over a broad range of frequencies. Equally important for future applications is the fact that the influence of optical backscatter, which dominates at low frequencies, has been well understood.
The team believes it now knows enough to responsibly design a potential future upgrade to Advanced LIGO which would use squeezing to improve the design's sensitivity. This is a true milestone and a wonderful example of forward-looking R&D that also acts to reduce risk for Advanced LIGO.
A further refinement of the H1 squeezed interferometer is underway: the installation of a low-loss output mode cleaner. Its objective is to achieve a greater reduction in noise and to provide further data on backscatter. This work will be pursued as a target of opportunity in the remaining available time, but the squeezing team can already claim success in its original goals.
The Advanced LIGO team has been working carefully around the H1 interferometer as it installs the new system. With the squeezing goals met, we can plan the decommissioning of H1 in preparation for the Advanced LIGO components. Our schedule calls for this to begin November 30, 2011, or shortly thereafter. That will mark the definitive end of the squeezing R&D on the Hanford 4km interferometer.
- Contributed by Dave Reitze