Collaborative Research: Stanford-Florida Program in Support of LIGO on Coatings and Core Optics

2015年，科学家们探测到了被称为引力波的时空涟漪，这是由两个黑洞合并产生的，这开启了引力波天文学领域。先进LIGO探测器灵敏度的提高使这场革命成为可能。计划未来的升级，以提高探测器的灵敏度将需要减少热噪声反射镜涂层，用于探测器的光学。这些改进将继续影响引力波天文学至少20年。一项名为A-sharp的升级计划旨在将镜面涂层的热噪声减少至少一半。开发较低热噪声涂层的挑战需要在理解非晶氧化物材料的物理学方面取得进展，这是该合作项目的核心研究重点。这项合作汇集了斯坦福大学和佛罗里达这项研究的实验和理论方面的专家。其目标是创建满足未来LIGO探测器使用的必要标准的反射镜涂层。该团队将继续通过其多学科活动和外展活动培养下一代STEM研究人员和专业人士。未来计划对LIGO进行的升级将寻求安装具有进一步改进涂层的镜子，特别是具有较低的布朗热噪声（BTN），这是限制探测器灵敏度的关键噪声源。潜在的A-sharp升级的基线设计要求涂层热噪声相对于Advanced LIGO +（A+）水平至少降低两倍。斯坦福-佛罗里达计划和涂料研究中心（CCR）之间的协同作用在以前的支持下取得了相当大的进展。基于X射线散射和原子结构建模的表征，确定了室温机械损耗与边缘和面共享多面体结构图案之间的联系，该团队提出了Ti掺杂的GeO 2作为高折射率低机械损耗涂层。CCR和LIGO实验室随后的实验工作支持了这一鉴定，导致A+反射镜选择了这种材料。在此奖项下进行的研究建立在这些结果的基础上，目标是找到涂层解决方案，进一步降低镜面升级和/或A-sharp系统的热噪声。该小组将与沉积小组反复合作开发非晶涂层，既利用从它们存款的材料中生成的数据来完善原子结构模型，又根据原子结构和建模工作的结果为这些小组提供合成活动的下一步指导。虽然我们工作的主要部分将仍然集中在非晶涂层上，该小组还将继续通过表征光吸收和开发双折射模型以及观察到的超出预期布朗贡献的过量噪声来为晶体AlGaAs涂层做出贡献。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估而被认为值得支持。

In 2015, scientists detected ripples in spacetime called gravitational waves, created by two black holes merging, which launched the field of gravitational-wave astronomy. Improvements in the sensitivity in the Advanced LIGO detectors made this revolution possible. Planned future upgrades to improve detector sensitivity will require reduced-thermal-noise mirror coatings that are used in the detector optics. These improvements will continue to impact gravitational-wave astronomy for at least 20 years. A planned upgrade called A-sharp aims to reduce the thermal noise from the mirror coatings by at least half. The challenge of developing lower thermal noise coatings requires progress in the understanding of the physics of amorphous oxide materials, which is the core research focus of this collaborative project. The collaboration brings together experts in both experimental and theoretical aspects of this research at Stanford University and the University of Florida. The goal is to create mirror coatings that meet the necessary standards for use in future LIGO detectors. The team will continue to train the next generation of STEM researchers and professionals through their multidisciplinary activities and outreach activities.Future planned upgrades to LIGO will seek to install mirrors with further improved coatings, in particular with lower Brownian thermal noise (BTN), which is a key noise source limiting detector sensitivity. The baseline design for the potential A-sharp upgrade calls for a coating thermal noise reduced by a factor of at least two with respect to Advanced LIGO + (A+) levels. Synergies between the Stanford-Florida program and the Center for Coatings Research (CCR) have enabled considerable progress under previous support. Having identified, based on characterization via X-ray scattering and atomic structure modeling, the connection between room-temperature mechanical losses and edge- and face-shared polyhedral structural motifs, the team proposed Ti-doped GeO2 as a high refractive-index low-mechanical-loss coating. Subsequent experimental work in the CCR and LIGO Lab supported this identification, leading to the selection of this material for the A+ mirrors. The research conducted under this award builds on these results, with a goal of finding coating solutions with a further factor of two reduction in thermal noise for mirror upgrades and/or an A-sharp system. The group will work iteratively with deposition groups developing amorphous coatings, both refining the atomic structure models with data generated from the materials they deposit, and by providing those groups with guidance for next steps in their synthesis campaigns based on the results from the atomic structure and modeling efforts. While the major portion of our work will remain focused on amorphous coatings, the group will also continue to contribute to crystalline AlGaAs coatings by characterizing optical absorption and developing models for birefringence and observed excess noise above the expected Brownian contribution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.