Laser noise mitigation through time delay interferometry for space-based gravitational wave interferometers using the UF laser interferometry simulator

The existence of gravitational waves was theorized in 1916 by Albert Einstein in accordance with the linearized theory of general relativity. Most experiments and observations to date have supported general relativity, but now, nearly 100 years later, the scientific community has yet devise a method to directly measure gravitational radiation. With the first attempts towards a gravitational wave measurement in the 1960s, many methods have been proposed and tested since then, all failing thus far to provide a positive detection. The most promising gravitational radiation detection method is through the use of a space-based laser interferometer and with the advancement of modern technologies, these space-based gravitational wave measurements will eventually provide important scientific data to physics, astro-physics, and astronomy communities.;The Laser Interferometer Space Antenna (LISA) is one such space-based laser interferometer. LISA’s proposed design objective is to measure gravitational radiation in the frequency range from 30 µHz to 1 Hz using a modified Michelson interferometer. The interferometer arms are 5 Gm in length measured between each of the 3 spacecraft in the interferometer constellation. The differential arm-length will be measured to an accuracy of 18 pm/ Hz resulting in a baseline strain sensitivity of 3.6 × 10 –21 / Hz . Unfortunately, the dynamics of the spacecraft orbits complicate the differential arm-length measurements. The arms of the interferometer change in length resulting in time-dependent, unequal arm-lengths and laser Doppler shifts. Thus, to cancel the laser noise, laser beatnotes are formed between lasers on separate SC and, using these one-way laser phase measurements, one can reconstruct an equal-arm interferometer in post-processing. This is commonly referred to as time-delay interferometry (TDI) and can be exploited to cancel the laser phase noise and extract the gravitational wave (GW) induced arm-length strain.;The author has assisted in the development and enhancement of The University of Florida Laser Interferometry Simulator (UFLIS) to perform more accurate LISA-like simulations. UFLIS is a hardware-in-the-loop simulator of the LISA interferometry system replicating as many of the characteristics of the LISA mission as possible. This includes the development of laser pre-stabilization systems, the modeling of the delayed inter-SC laser phase transmission, and the µcycle phase measurements of MHz laser beatnotes.;The content of this dissertation discusses the general GW detection methods and possible GW sources as well as the specific characteristics of the LISA mission’s design. A theoretical analysis of the phasemeter and TDI performance is presented along with experimental verification measurements. The development of UFLIS is described including a comparison of the UFLIS noise sources with the actual LISA mission. Finally, the enhanced UFLIS design is used to perform a second-order TDI simulation with artificial GW injection. The results are presented along with an analysis of relevant LISA characteristics and GW data-extraction methods.