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，旨在了解原子水平上光学涂层材料中热噪声的物理起源，并为复合非晶氧化物（二氧化硅，二氧化钛，钽，氧化物等）中金属元素的最佳比例提供指导。由原子在有限温度下运动引起的热噪声会影响超高分辨率干涉仪的性能，例如激光干涉仪引力波天文台（LIGO）中使用的激光干涉仪，并且LIGO科学合作组织（LSC）对此特别感兴趣。该项目将为计算物理学的研究生提供严格的培训。PI与许多国际实验和计算材料物理小组合作，包括英国格拉斯哥的一个小组，瑞士联邦理工学院苏黎世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Colombi，讨论有关大型结构模拟的问题。LSC是一个国际组织。它也与其他专注于引力波观测的组织有着密切的关系。光学组在LIGO会议上与其他引力组织（VIRGO，AGO等）联合组织焦点会议。先进LIGO是LIGO的主要升级，预计将受到最关键的~50-150 Hz频段的热噪声的限制，而几种最先进的稳频系统的性能受到低至几Hz频率的热噪声的限制。该项目还研究了晶体材料（GaAs/AlGaAs和GaP/AlGaP）的机械性能，这是一种新的光学涂层范例，已在实验中得到证实。改进电介质涂层和降低热噪声在许多高精度光学测量中有着远远超出LIGO的应用，例如时间和频率测量，等效原理的测量等。表征非晶材料的计算方法也将有助于许多其他领域，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.