Experiments and Simulations for Improving the Sensitivity of Advanced LIGO and Future Gravitational Wave Detectors

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The first detection of gravitational waves by Advanced LIGO in 2015 marked the dawn of the era of gravitational wave astronomy. Since then Advanced LIGO has continued to provide fascinating insights into the nature of our universe; confirming the existence of several merging black hole binary systems, as well as detecting gravitational waves from a neutron star inspiral and merger in parallel with electromagnetic observations. In spite of these incredible achievements (recognized with awards including the Nobel Prize in Physics), Advanced LIGO is not yet operating at its predicted maximum sensitivity. This award supports research in the form of experiments and simulations towards improving the sensitivity of Advanced LIGO, with the aim of detecting gravitational wave events more often and with higher signal-to-noise ratios. Higher sensitivity observations will increase the scientific yield of observing runs, allowing us to make stronger statements about the nature of gravity, the composition of neutron stars, and the formation history of black holes in our universe. This award also supports research into technology for gravitational wave detectors beyond Advanced LIGO, so that the scientific community can be prepared to build the detectors of the future with the best possible design and components. Much of the supported work will be performed by undergraduate students, postgraduate students and recent PhD graduates. This will provide an excellent training opportunity for these junior scientists, allowing them to gain valuable skills and experience, while also serving to bolster the scientific workforce in the USA.This award supports several experimental programs aimed at developing specific technologies for potential use in Advanced LIGO and future gravitational wave detectors. All interferometric gravitational wave detectors employ schemes to manage wavefront distortions in the laser beams that probe the position of the test masses, which can limit the sensitivity of detectors in several ways. Wavefront distortions will become even more critical as squeezed light technology is employed in order to reduce the quantum noise limit of the detectors. An experimental program will be carried out to investigate new ways to sense these distortions as they arise, in order that they can be corrected before they negatively impact the detector sensitivity. Another experimental program performed under this award will develop a new alignment sensing technique, which has the potential to simplify the optical layout of gravitational wave detectors and reduce the misalignment driven noise. An experimental investigation will also be pursued to determine the feasibility of using non-traditional laser beam shapes in order to reduce the effects of mirror thermal noise on interferometer sensitivity. This award also supports the development and use of laser interferometer simulation tools for characterizing and improving the operation of the Advanced LIGO detectors. Simulations have often played a key role in understanding the limiting noise sources in interferometers, and can be used to provide rapid tests of potential solutions before their often costly and time-intensive implementation in real detectors. The work performed under this award will also look beyond Advanced LIGO to near-term upgrades and longer-term new detectors, using similar simulations to help in the design and optimization of these new, more sensitive machines.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.