Experiments Towards the Development of a Laser Suitable for an Interferometric Gravitational Wave Detector

Carmichael, Allan (1992) Experiments Towards the Development of a Laser Suitable for an Interferometric Gravitational Wave Detector. PhD thesis, University of Glasgow.

Abstract

Gravitational waves are distortions in the curvature of space-time. They were predicted by Einstein in 1916 but it is only since the early 1960's that experimental progress has been made towards the detection of gravitational waves. The most probable sources are astrophysical in nature; the detection of gravitational radiation will open up a new field of observational astronomy. The research group at Glasgow has been developing a technique to detect gravitational waves using optical interferometry. The technique is based on a Michelson interferometer. The gravitational waves cause a differential displacement of the interferometer arms and the subsequent phase change of the laser light in the orthogonal arms is detected as an intensity change. In order to have a good chance of detecting some astrophysical sources an interferometer arm length of around 1 km is required. Such long base line detectors need to be operated with a laser source of around 100 W of frequency and intensity stabilised light. Chapter 1 is a general introduction to gravitational waves. A review of sources is given and this is followed by descriptions of the two main terrestrial detection techniques; bar detectors and interferometric detectors. Chapters 2 to 7 describe experiments towards the development of a laser capable of supplying around 100 W of frequency and intensity stabilised light. Chapters 2 and 4 describe a diode pumped Nd:YAG laser and a flashlamp pumped Nd:YAG laser respectively. An interferometer can be operated with infrared light and so both of these lasers are potential sources as they stand (if developed further). However, engineering problems can be avoided if visible light is used: the diffraction is less and so the vacuum pipes are smaller. Chapter 6 describes the conversion of the flashlamp pumped laser to operate at the second harmonic. The nonlinear susceptibility of KTP is used to generate the second harmonic. Chapters 3, 5 and 7 describe techniques that can be applied to improve the characteristics of frequency and intensity stability of a laser or describe the experimental measurements of the laser characteristics (frequency stability and intensity) that are particularly important to interferometric detectors. These include injection locking, servo control to remove intensity noise, frequency noise measurement and the generation of a second harmonic error signal for frequency stabilisation.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Astrophysics, Astronomy
• Date of Award: 1992
• Depositing User: Enlighten Team
• Unique ID: glathesis:1992-78412
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 28 Feb 2020 12:09
• Last Modified: 28 Feb 2020 12:09
• URI: https://theses.gla.ac.uk/id/eprint/78412