Impact and mitigation of wavefront distortions in precision interferometry

Jones, Aaron ORCID: 0000-0002-0395-0680 (2020). Impact and mitigation of wavefront distortions in precision interferometry. University of Birmingham. Ph.D.

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Abstract

Wavefront distortions, arising from mismatches, degrade quantum noise mitigation strategies in precision metrological devices, such as LIGO. Direct mode decomposition quantifies wavefront distortions in terms of solutions to the paraxial wave equation. The first part of this thesis develops high dynamic range mode decomposition, by using photodiode readout and developing novel alignment strategies. Limiting noise sources are suppressed and the noise performance is characterized in the 1\,mHz to 10\,kHz frequency range.

Higher order, Hermite-Gauss, spatial modes may be used in precision metrology to sidestep thermal noise. This thesis demonstrates the production of higher order, Hermite-Gauss spatial modes, but, also finds that these modes are more susceptible to mode mismatch losses than the fundamental mode.

Another form of precision metrology is atomic interferometry. Optical cavities reject wavefront distortions in the laser beams used to manipulate the atoms; however, they introduce an elongation of the beam-splitter pulses. A numerical study finds that this elongation suppresses the atomic excitation probability, when the transition is not exactly on resonance, reducing atomic flux. Long baseline, high finesse resonators are particularly affected.

The closing section of this thesis describes a tool used to validate numerical models used throughout this work.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):