NSF Award
2207858
The Laser Interferometer Gravitational-wave Observatory(LIGO) project has given scientists the ability to observe the universe in a completely new way. Unlike conventional telescopes, which use the light emitted by stars and galaxies to learn their properties and their place in the universe, GW detectors use gravitational waves (GW), which are similarly emitted by many astrophysical objects. Gravitational waves are ripples in spacetime that travel to Earth and cause the detectors to essentially change in size. To observe this change The LIGO detectors require state-of-the-art mirrors, which are used to sense the stretching and contraction of space and time. Improvements in mirror design will allow observers to look further into space and detect more of these GW signals. The proposed project will aid in pushing the mirror technology by utilizing light scattering as a tool to study mirror coatings. Specifically, an important aspect of the quality of a mirror is the presence of defects which scatter light and inhibit the operation of the LIGO detectors. In addition, defects may sometimes develop on the mirror surface with time, but the process is not always understood. This research project is designed to study defects on mirrors so that it will be possible to ultimately improve LIGO’s sensitivity. The work will be carried out with the engagement of undergraduate and high school students, which will provide invaluable experience as they pursue their career in technology and academia.<br/><br/>Coating thermal noise and scattering phase noise are sources of noise responsible for limiting LIGO's sensitivity at low to moderately low frequencies and arise from the optical properties of the mirror coatings. Mitigation of coating thermal noise requires the development of a coating with low mechanical loss, while at the same time satisfying the stringent requirements for scattering and absorption set by GW detectors. In addition, it is necessary to understand the development of defects on the mirrors that degrade its scattering and absorption characteristics. This work will address such questions in a systematic way by studying the scattering properties of samples of novel coatings as well as samples already used in GW detectors. The PI will utilize light scattering in a way that is not being utilized currently, studying in detail the radiation patterns of individual defects. Specifically, the PI will use light scattering measurements from mirrors to study various aspects of new and existing mirror coatings. Studies include i) scattering properties from newly designed coatings, ii) scattering properties of defects and surfaces, iii) formation of defects on mirrors through contamination or aging, and iv) scattering from mirrors as a function of annealing temperature and coating thickness. The project also includes a feasibility study for a novel beam tracking method for GW detectors using scattering.<br/><br/>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.
