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# Precision interferometry in a new shape: higher-order Laguerre-Gauss modes for gravitational wave detection

Fulda, Paul (2012)
Ph.D. thesis, University of Birmingham.

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## Abstract

The sensitivity of the next generation of interferometric gravitational wave detectors will be limited in part by thermal noises of the optics. It has been proposed that using higher-order Laguerre-Gauss (LG) beams in the interferometers can reduce this noise. This thesis documents progress made in assessing the compatibility of higher-order LG beam technology with the existing precision interferometry framework used in the gravitational wave detector community. A numerical investigation was made into techniques for generating higher-order LG modes with a phase modulating surface. The optimal conditions for mode conversion were determined using fast Fourier transform (FFT) simulations, and predictions were made for the mode purity achievable with this method. Table-top experiments performed at Birmingham demonstrated the generation of higher-order LG modes using a spatial light modulator, and showed for the first time the feedback control of an optical cavity on resonance for higher-order LG modes. An increase in the purity of LG$$_{33}$$ modes from 51% to over 99% upon transmission through the cavity was shown. Investigations were carried out at the Glasgow 10m prototype detector into the performance of the LG$$_{33}$$ mode in a suspended 10m cavity, providing useful insights into the compatibility of LG modes with larger scale interferometers.

Type of Work: Ph.D. thesis. Freise, Andreas Colleges (2008 onwards) > College of Engineering & Physical Sciences Astrophysics and Space Research Group, School of Physics and Astronomy QB AstronomyQC PhysicsT Technology (General) University of Birmingham 3703
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