Coatings for Next Generation Gravitational Wave Interferometers

该奖项支持相对论和相对论天体物理学的研究，并解决了NSF“宇宙之窗”大理念的优先领域。2015年，位于路易斯安那州利文斯顿和华盛顿汉福德的双激光干涉引力波天文台（LIGO）探测器首次探测到两个大质量黑洞碰撞产生的引力波，不仅证实了爱因斯坦关于引力波存在的预测，而且还批准了多年来在引力波探测器（GWD）开发方面的努力。引力波探测器是一种干涉仪，其中强激光束在两组正交臂的反射镜之间反射。引力波会导致两个干涉仪臂之间激光束的路径长度不同，从而产生一个独特的干涉图案，当分析时，可以识别产生它们的事件。GWD的探测灵敏度取决于各种噪声源，其中干涉仪反射镜涂层的热噪声是一个主要组成部分。在干涉仪反射镜的高反射率非晶氧化物涂层中的热噪声会导致路径长度的差异，从而掩盖引力波的信号。为了提高目前GWD的灵敏度和满足未来GWD的需求，必须共同努力来理解和控制非晶氧化物涂层中引起热噪声的机制。这些项目将为不同的研究生群体提供机会，深入了解影响非晶材料内部摩擦的物理机制，同时获得光学科学方面的宝贵专业知识。这个跨学科的研究项目将培养具有宝贵技能的学生，为学术、国家实验室和工业环境中的科学技术进步做出贡献。PI的团队最近取得了突破性的成果。 他们已经确定了二氧化钛和二氧化锗的混合物，其内部耗散率为0.0001。 相对于现有技术的材料，这种低水平的机械损失可以提供布朗噪声水平的几乎两倍的改进。这些结果将使我们有可能生产出满足先进LIGO探测器计划升级的热噪声要求的反射镜。 该团队将研究TiO2掺杂GeO2中导致如此低的机械损耗的基本机制，并实施进一步降低机械损耗的策略。该团队还将研究薄膜的光学特性，以满足Advanced LIGO探测器对涂层的严格吸收损耗要求。 基于这些优化材料的多层介电涂层将通过离子束溅射沉积，并以其布朗噪声为特征，布朗噪声的降低极大地影响了引力波探测器的灵敏度。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，被认为值得支持。

This award supports research in relativity and relativistic astrophysics and it addresses the priority areas of NSF's "Windows on the Universe" Big Idea. The first detection of gravitational waves from the collision of two massive black holes by the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors in Livingston, Louisiana, and Hanford, Washington in 2015 not only confirmed Einstein's predictions of the existence of gravitational waves but also ratified years of efforts in the development of gravitational wave detectors (GWD). Gravitational wave detectors are interferometers in which an intense laser beam bounces between two sets of mirrors in orthogonal arms. Gravitational waves cause differences in the path length of the laser beam between the two interferometer arms, giving rise to a distinct interference pattern that when analyzed identifies the event that created them. The detection sensitivity of GWD is determined by various noise sources, among which thermal noise of the coatings in the mirrors of the interferometer is a main component. Thermal noise in the high reflectance amorphous oxide coatings in the interferometer's mirrors causes path length differences that can mask the signals from gravitational waves. To increase the sensitivity of present GWD and meet the demands of future GWD, a concerted effort to understand and control the mechanisms that give rise to thermal noise in amorphous oxide coatings is imperative. The projects will offer a diverse group of graduate students opportunities to gain in-depth understanding of the physical mechanisms that affect internal friction in amorphous materials and at the same time gain valuable expertise in optical sciences. This interdisciplinary research project will train students with valuable skills to contribute to advance science and technology in academic, national laboratory and industrial settings.The PI's team has recently achieved a breakthrough result. They have identified mixtures of titanium dioxide and germanium dioxide that show internal dissipations at a level of 0.0001. Such a low level of mechanical loss can provide for an almost a factor of two improvement on the level of Brownian noise with respect to the state-of-the-art materials. These results will make it possible to produce the mirrors that will meet the thermal noise requirements for the planned upgrades of the Advanced LIGO detectors. The team will investigate the fundamental mechanisms in TiO2 doped GeO2 that lead to such low mechanical loss and implement strategies to further reduce it. It will also investigate the optical properties of thin films to meet the stringent absorption loss requirements of the coatings for Advanced LIGO detectors. Multilayer dielectric coatings based on these optimized materials will be deposited by ion beam sputtering and characterized for their Brownian noise, which reduction greatly impacts the sensitivity of gravitational wave detectors.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.