2026-09-20T12:12:41Zhttps://digital.library.adelaide.edu.au/server/oai/request

oai:digital.library.adelaide.edu.au:2440/1363432022-09-08T06:28:33Zcom_2440_14759col_2440_14760

Ottaway, David Brown, Daniel Veitch, Peter Ciobanu, Alexei School of Physical Sciences 2021 https://hdl.handle.net/2440/136343 The Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO) directly detected gravitational waves for the first time on the 14th of September 2015. In 2017 the detection of gravitational waves from a binary neutron star merger was subsequently followed up by observations by optical and radio astronomers — the first time an astrophysical event was observed by two completely separate astrophysical signals. This marked the beginning of multi-messenger astronomy. Since then 90 astrophysical events have been observed using gravitational waves. To increase the rate of event detection the sensitivity of gravitational wave detectors must be improved. Current state of the art gravitational wave detectors are optical interferometers in the dual recycled Fabry-Perot Michelson (DRFPMI) configuration with quantum squeezed light injected to reduce vacuum noise. Future plans to improve the sensitivity further rely on increasing the circulating laser power and improving the efficiency of quantum squeezing. Squeezing efficiency is drastically reduced by optical losses in the interferometer of which mode mismatch is a large component. Higher laser power introduces larger thermal distortions in the interferometer, which increase mode mismatch. This thesis covers topics relevant to optical modelling of coupled cavity interferometers such as the DRFPMI with a focus on mode mismatch. Novel applications in aLIGO commissioning based on existing mode mismatch sensing techniques using the output mode cleaner (OMC) are presented. A new mode mismatch sensing technique based on transverse higher order mode sidebands is demonstrated on an optical tabletop and its applications to mode mismatch sensing in aLIGO is discussed. A new optical modelling framework based on linear canonical transformations and signal flow graph theory is also presented. Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 2022 en Gravitational waves Interferometry Lasers Optics Optical models Mode matching Wavefront modelling and sensing for advanced gravitational wave detectors Thesis This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legalsopen.access