Understanding and Reducing Thermal Noise via Atomistic Simulations

该奖项支持在原子水平上理解光学涂层材料中热噪声的物理起源的理论努力。热噪声会影响超高精度干涉仪的性能，例如在激光干涉仪引力波天文台（LIGO）中使用的干涉仪。 这项研究的目的是通过研究各种非晶涂层材料的机械性能，以及使用大规模计算掺杂（即混合在其他氧化物）的影响，原子模型的发展。该研究将与LIGO科学合作组织的光学工作组协调。该工作计划有三个主要部分：1）了解熔融二氧化硅中的热噪声，2）了解分层薄膜（例如氧化钽-二氧化硅）中缺陷、掺杂和界面的影响，以及3）网络设计具有最佳性能的材料。热噪声是涂层材料内部机械相互作用释放的能量。LIGO实验人员正在通过测量各种涂层材料（如二氧化硅，二氧化钛，钽和铪）中的机械损失来解决这个问题。这项研究将提供一个更系统的涂层材料的方法的基础，因为，目前，很少有人知道那些微观内部过程的玻璃材料，导致机械损失。本项目中这些材料的理论研究将为未来的实验提供信息。改进介电涂层和降低热噪声在许多高精度光学测量中的应用远远超出了LIGO。表征非晶材料的计算方法也将对许多其他领域，如纳米科学，材料科学和生物科学有用。该项目将为计算物理学的研究生和博士后研究人员提供严格的培训。

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.