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

2015年，科学家探测到两个黑洞合并产生的时空涟漪，称为引力波，这开启了引力波天文学领域。先进的LIGO探测器灵敏度的提高使这场革命成为可能。为了提高探测器的灵敏度，计划未来的升级将需要在探测器光学中使用降低热噪声的反射镜涂层。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的升级计划旨在将反射镜涂层的热噪声减少至少一半。开发低热噪声涂层的挑战需要在理解非晶氧化物材料的物理特性方面取得进展，这是本合作项目的核心研究重点。此次合作汇集了斯坦福大学和佛罗里达大学的实验和理论方面的专家。其目标是制造出符合未来LIGO探测器所需标准的镜面涂层。该团队将继续通过多学科活动和外展活动培养下一代STEM研究人员和专业人员。未来计划升级的LIGO将寻求安装具有进一步改进涂层的镜子，特别是具有更低的布朗热噪声（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将涂层热噪声降低至少两倍于高级LIGO + (a +)水平。斯坦福-佛罗里达项目和涂层研究中心（CCR）之间的协同作用在之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，该团队确定了室温机械损耗与边缘和面共享多面体结构基元之间的联系，并提出了ti掺杂的GeO2作为高折射率低机械损耗涂层。随后在CCR和LIGO实验室进行的实验工作支持了这一鉴定，从而选择了这种材料作为A+反射镜。根据该奖项进行的研究基于这些结果，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。该小组将迭代地与沉积小组合作开发非晶涂层，既可以通过沉积材料生成的数据来完善原子结构模型，也可以根据原子结构和建模工作的结果为这些小组的合成活动的下一步提供指导。虽然我们的主要工作仍将集中在非晶涂层上，但该小组也将继续通过表征光学吸收和开发双折射模型来为晶体AlGaAs涂层做出贡献，并观察到超出预期布朗贡献的多余噪声。该奖项反映了美国国家科学基金会的法定使命，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，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.