Mirror, mirror on the wall: pushing the boundaries of gravitational-wave detection

This thesis investigates materials for improving the sensitivity of gravitational-wave detectors. Gravitational waves are ripples in spacetime generated by the collision of massive objects like black holes. Detecting them requires extremely sensitive instruments like laser interferometers. This work discusses interferometer noise sources, with a particular interest on thermal noise. It delves into the critical role of mirror components focusing on the fundamental physics of energy dissipation within materials, emphasizing the concept of mechanical loss. A significant part of this work involved the development and implementation of the Gentle Nodal Suspension system, an experimental setup designed for measuring the mechanical loss in the materials. Utilizing this system, this research investigated several promising coating materials, and among them, TiO2:SiO2 coatings exhibited a a significant reduction in thermal noise compared to existing options, highlighting their potential for enhancing the sensitivity of gravitational-wave detectors. The final part of this research investigates thermoelastic loss in high-index glass mirrors, exploring the impact of different geometries on this phenomenon. This work contributes significantly to the development of advanced materials for gravitational-wave detectors, investigating different coating materials, pioneering novel measurement techniques, and advancing our understanding of material properties and their deep impact on detector sensitivity.