Understanding and Reducing Thermal Noise via Atomistic Simulations

该研究项目是一项面向计算的理论工作，旨在从原子水平上了解光学涂层材料中热噪声的物理来源，并为复合无定形氧化物(二氧化硅、二氧化钛、钽酸、哈夫尼亚等)中金属元素的最佳比例提供指导。有限温度下原子运动引起的热噪声影响超高分辨率干涉仪的性能，如激光干涉仪引力波天文台(LIGO)中使用的激光干涉仪，这是LIGO科学合作(LSC)特别关注的问题。该项目将为研究生提供计算物理方面的严格培训。PI与多个国际实验和计算材料物理小组进行了合作，其中包括英国格拉斯哥大学苏黎世理工学院的一个小组和上海复旦大学的一个小组。她还访问了巴黎天体物理研究所的科伦比，讨论有关大结构模拟的问题。LSC是一个国际组织。它还与专注于引力波观测的其他组织保持着密切的关系。光学小组与其他引力组织(处女座、AGO等)联合在LIGO会议上组织焦点会议。高级LIGO是LIGO的主要升级，预计将在最关键的~50-150 Hz频段受到热噪声的限制，而几种最先进的频率稳定系统的性能在低至几赫兹的频率下受到热噪声的限制。本项目还研究了晶体材料(GaAs/AlGaAs和GaP/AlGaP)的力学性能，这是一种已被实验证明的光学镀膜的新范例。改进介质涂层和降低热噪声在许多远远超出LIGO的高精度光学测量中有应用，例如时间和频率测量、等效原理测量等。表征非晶态材料的计算方法也将对许多其他领域有用，如纳米科学、材料科学和生物科学。

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.