Understanding and Reducing Thermal Noise via Atomistic Simulations

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This award supports a theoretical effort to understand the physical origin of thermal noise in optical coating materials at the atomic level. Thermal noise can affect the performance of ultra high-precision interferometers such as employed in the Laser Interferometer Gravitational- Wave Observatory (LIGO). This research will aim at development of atomistic models for various amorphous coating materials through investigation of the mechanical properties, as well as the effects of doping (i.e. mix-in other oxides) using large-scale computation. The research will be coordinated with the Optics Working Group of the LIGO Scientific Collaboration. The work plan has three major parts: 1) Understanding thermal noise in fused silica, 2) understanding effects of defects, doping, and interfaces in layered films such as tantala-silica, and 3) cyber-designing materials with optimal properties. Thermal noise is the energy released by mechanical interactions inside the coating materials. LIGO experimenters are approaching this problem empirically by measuring these mechanical losses in various coating materials such as silica, titania, tantala, and hafnium. This research would provide the basis for a more systematic approach for coating materials since, currently, very little is known about those microscopic internal processes of glassy materials that lead to mechanical losses. The theoretical studies of these materials in this project will inform future experiments. Improving dielectric coatings and reducing thermal noise has applications in many high precision optical measurements far beyond LIGO. The computational approach of characterizing amorphous materials will also be useful to many other areas such as nano-scale science, material science, and bio-science. The project will provide rigorous training for graduate students and postdoctoral researchers in computational physics.