RUI: Light Scattering Metrology for Gravitational Wave Optics

激光干涉仪引力波天文台(LIGO)项目为科学家提供了以一种全新的方式观察宇宙的能力。与传统的望远镜不同，传统的望远镜使用恒星和星系发出的光来了解它们的性质和它们在宇宙中的位置，GW探测器使用的是引力波(GW)，许多天体物理物体类似地发射引力波(GW)。引力波是时空中的涟漪，传播到地球，导致探测器的大小发生本质上的变化。为了观察这种变化，LIGO探测器需要最先进的镜子，用来感知空间和时间的拉伸和收缩。镜面设计的改进将使观测者能够更深入地观察太空，并探测到更多这样的GW信号。拟议的项目将有助于通过利用光散射作为研究镜面涂层的工具来推动镜面技术。具体地说，反射镜质量的一个重要方面是存在散射光并抑制LIGO探测器运行的缺陷。此外，随着时间的推移，镜面上有时会出现缺陷，但其过程并不总是被理解。该研究项目旨在研究反射镜上的缺陷，以便有可能最终提高LIGO的灵敏度。这项工作将在本科生和高中生的参与下进行，这将为他们在技术和学术领域的职业生涯提供宝贵的经验。镀膜热噪声和散射相位噪声是噪声源，导致LIGO在低到中等低频下的灵敏度受到限制，并源于镜面涂层的光学特性。要降低涂层的热噪声，需要开发一种机械损耗低的涂层，同时满足GW探测器对散射和吸收的严格要求。此外，有必要了解反射镜上缺陷的发展，这些缺陷降低了反射镜的散射和吸收特性。这项工作将通过研究新型涂层的样品以及已经用于GW探测器的样品的散射特性来系统地解决这些问题。PI将以目前尚未使用的方式利用光散射，详细研究单个缺陷的辐射模式。具体地说，PI将使用镜面的光散射测量来研究新的和现有的镜面涂层的各个方面。研究包括i)新设计的涂层的散射特性，ii)缺陷和表面的散射特性，iii)由于污染或老化而在反射镜上形成缺陷，以及iv)反射镜的散射随退火温度和涂层厚度的变化。该项目还包括一项对使用散射的GW探测器的新型光束跟踪方法的可行性研究。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Laser Interferometer Gravitational-wave Observatory(LIGO) project has given scientists the ability to observe the universe in a completely new way. Unlike conventional telescopes, which use the light emitted by stars and galaxies to learn their properties and their place in the universe, GW detectors use gravitational waves (GW), which are similarly emitted by many astrophysical objects. Gravitational waves are ripples in spacetime that travel to Earth and cause the detectors to essentially change in size. To observe this change The LIGO detectors require state-of-the-art mirrors, which are used to sense the stretching and contraction of space and time. Improvements in mirror design will allow observers to look further into space and detect more of these GW signals. The proposed project will aid in pushing the mirror technology by utilizing light scattering as a tool to study mirror coatings. Specifically, an important aspect of the quality of a mirror is the presence of defects which scatter light and inhibit the operation of the LIGO detectors. In addition, defects may sometimes develop on the mirror surface with time, but the process is not always understood. This research project is designed to study defects on mirrors so that it will be possible to ultimately improve LIGO’s sensitivity. The work will be carried out with the engagement of undergraduate and high school students, which will provide invaluable experience as they pursue their career in technology and academia.Coating thermal noise and scattering phase noise are sources of noise responsible for limiting LIGO's sensitivity at low to moderately low frequencies and arise from the optical properties of the mirror coatings. Mitigation of coating thermal noise requires the development of a coating with low mechanical loss, while at the same time satisfying the stringent requirements for scattering and absorption set by GW detectors. In addition, it is necessary to understand the development of defects on the mirrors that degrade its scattering and absorption characteristics. This work will address such questions in a systematic way by studying the scattering properties of samples of novel coatings as well as samples already used in GW detectors. The PI will utilize light scattering in a way that is not being utilized currently, studying in detail the radiation patterns of individual defects. Specifically, the PI will use light scattering measurements from mirrors to study various aspects of new and existing mirror coatings. Studies include i) scattering properties from newly designed coatings, ii) scattering properties of defects and surfaces, iii) formation of defects on mirrors through contamination or aging, and iv) scattering from mirrors as a function of annealing temperature and coating thickness. The project also includes a feasibility study for a novel beam tracking method for GW detectors using scattering.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.