LIGO Document T2200203-v2

Optical contact bonding for mitigating clamping losses in silicon resonators

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T - Technical notes
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This experiment aims to improve the quality factor of silicon resonators in order to mitigate the thermal noise present in the mirror coatings and suspension systems in the LIGO Michelson Interferometer. The oscillation of the cantilever is analyzed and used to calculate the mechanical quality factor through the exponential decay of the oscillations with the ringdown method. The clamping losses among other extrinsic sources of loss are studied to understand the dissipation mechanisms affecting the quality factor. The design of the clamp was made to use optically contacted layers of silicon in order to reduce the acoustic waves radiating away from the resonator into the substrate, in order to increase the quality factor of the cantilever. The quality factor of the silicon cantilever with the optically contacted layers averages around 4 ∗ 10^3 which did not show improvement over the cantilever alone. The oscillation data that was collected had a weakened signal which skewed the calculations of the last ringdown data collection. It is possible that a better oscilloscope could improve the accuracy of the ringdown experiments and show that optical contacted layers of silicon decrease clamping losses. Further experimentation may show that thermoelastic losses is the dominant source of loss within the cantilever.
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Ojo Akinwale SURF 2022

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