Doctor of Philosophy (PhD)



Document Type



The Advanced LIGO (aLIGO) detectors use 1064 nm lasers to measure the tiny fluctuations in spacetime that occur when gravitational waves pass through the earth. LIGO makes use of advanced coating methods and materials to limit the amount of light that scatters from the main beam, but some amount of light does scatter. This stray light can interact with surfaces inside the interferometer that are not seismically isolated and then recombine with the main beam, introducing excess noise into the gravitational wave channel. This thesis reviews the methods for modeling scattered light with ray tracing software and analytical models, for measuring scattered light with driven measurements of the vacuum enclosure, and for mitigating scattered light with baffles and changes to interferometer controls. It also details the process for finding correlations with auxiliary sensors in order to locate the sources of scattered light noise. The results of this work are improved sensitivity of the LIGO detectors in the frequency band from 20 Hz up to 200 Hz.

Committee Chair

Giaime, Joseph