Understanding and Reducing Thermal Noise via Atomistic Simulations

The research project is a computational oriented theoretical effort that aims at understanding the physical origin of thermal noise in optical coating materials at the atomic level and providing guidance for the optimal ratio of metallic elements in composite amorphous oxides (silica, titania, tantala, hafnia etc). Thermal noise that is caused by atomic movement at finite temperature affects the performance of ultra high-resolution interferometers such as the laser interferometer employed in the Laser Interferometer Gravitational-Wave Observatory (LIGO) and is of special interest to the LIGO Scientific Collaboration (LSC). The project will provide rigorous training for graduate students in computational physics. The PI has collaborations with a number of international experimental and computational materials physics groups including a group at Glasgow UK, ETH Zurich, and a group at Fudan University Shanghai. She also visits Colombi at the Institute of Astrophysics Paris to discuss issues regarding large-structure simulations. The LSC is an international organization. It also has a tight relation with other organizations that focus on gravitational wave observations. The optical group organizes focus sessions at LIGO meetings jointly with other gravitational organizations (VIRGO, AGO etc.) and in independent workshops.

Advanced LIGO, the major upgrade of LIGO, is expected to be limited by thermal noise in the most critical ~50-150 Hz frequency band while the performance of several state-of-the art frequency stabilization systems is limited by thermal noise at frequencies as low as a few Hz. This project also studies mechanical properties of crystalline materials (GaAs/AlGaAs, and GaP/AlGaP), a new paradigm for optical coating that has been demonstrated experimentally. Improving dielectric coatings and reducing thermal noise have applications in many high precision optical measurements far beyond LIGO, such as time and frequency measurements, measurements of the equivalence principle, and many others. The computational approach of characterizing amorphous materials will also be useful to many other areas such as nano-scale science, materials science, and bio-science.