MRI: Track 1 Development of Large Optic Crystalline Coating Characterization Instrument (LOCCCI) for Gravitational Wave Detectors

该奖项支持相对论和相对论天体物理学的研究，它解决了NSF“宇宙之窗”大构想的优先领域。“引力波天体物理学是科学领域最令人兴奋的前沿之一，”美国国家科学院十年调查（2020年）指出。该奖项将有助于实现引力波探测器灵敏度的关键进步，并有助于解决过去二十年来限制该领域的噪声源。自2015年以来，激光干涉仪引力波天文台（LIGO）已经探测到90多个事件，包括双中子星和双黑洞系统的吸入和合并。最近对探测器的改进保证了每周都有新的观测结果。然而，LIGO的灵敏度仍然受到涂层热噪声（CTN）的限制。由该奖项资助的研究将使晶体反射镜涂层的发展成为可能，与目前的反射镜涂层相比，它可以将CTN降低10倍。灵敏度上的这一重大进步将使我们能够以更高的灵敏度探测到更多的事件。引力波观测为众多天文学家、物理学家、学生和公众提供了信息和启发。许多人对黑洞和中子星的观测很感兴趣，它们的魅力有助于提高公众的科学意识。该奖项将培养本科生和研究生的技能，这些技能可以应用于研究和更广泛的经济技术领域。该团队将继续努力工作，为历史上被剥夺公民权的群体提供这些机会。最后，本研究所获得的知识将推动引力波天体物理学、精密光学和低耗散材料材料科学等领域的发展。反射镜涂层热噪声（CTN）限制了当前干涉引力波探测器在中心频段（灵敏度最高的区域）的灵敏度。目前所有引力波探测器都使用离子束溅射（IBS）非晶态氧化物的镜面涂层技术，在过去的15年中，在减少产生CTN的弹性损失方面只取得了适度的进展。幸运的是，晶体GaAs/AlGaAs涂层（以下简称AlGaAs涂层）满足LIGO严格的光学要求，其CTN估计比目前先进的LIGO涂层低10倍。灵敏度的增加将产生事件率的急剧跃升，事件率随着灵敏度范围的立方而增加。它还将允许以非常高的信噪比观察附近的事件，这可能提供对中子星结构的见解和对广义相对论的额外测试。最后，晶体涂层超出了所有计划中的未来引力波探测器的要求。因此，该奖项资助了仪器仪表的进步，将使该领域受益数十年。然而，挑战仍然存在，因为AlGaAs涂层是双折射的，存在晶体缺陷，并且只能在小直径中制造。该奖项将资助LOCCCI仪器，该仪器将为引力波探测器开发低噪声、大直径、晶体涂层。LOCCCI仪器最初将用于在大直径（20厘米）上测试这些涂层的双折射噪声、晶体缺陷密度和表面均匀性。这项研究将为制造改进提供信息，并最终证明将在探测器中部署的30厘米涂层的开发是合理的。该仪器还将测试生产的涂料是否符合设计规范。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。

This award supports research in relativity and relativistic astrophysics, and it addresses the priority areas of NSF's "Windows on the Universe" Big Idea. "Gravitational wave astrophysics is one of the most exciting frontiers in science.” states the National Academy of Sciences Decadal Survey (2020). This award will help achieve a key advancement in sensitivity for gravitational wave detectors and help resolve a noise source that has limited the field for the past two decades. Since 2015, the Laser Interferometer Gravitational-wave Observatory (LIGO) has detected over 90 events, including the inspiral and coalescence of binary neutron star and binary black hole systems. The most recent improvements to the detector promise new observations on a weekly basis. Nevertheless, LIGO’s sensitivity remains limited by coating thermal noise (CTN). The research funded by this award will enable the development of crystalline mirror coatings, which could reduce CTN by a factor of 10 compared to the current mirror coatings. This significant advancement in sensitivity will allow the detection of many more events at much higher sensitivity. Gravitational wave observations have informed and inspired a broad range of astronomers, physicists, students, and the general public. Many people are intrigued by black hole and neutron star observations and their fascination helps raise the public’s scientific awareness. This award will train undergraduate and graduate students with skills that can be applied to research and to technical areas in the broader economy. The team will continue to work hard providing these opportunities to groups that have been historically disenfranchised. Finally, the knowledge gained in this research will advance the areas of gravitational wave astrophysics, precision optics, and the materials science of low-dissipation materials.Mirror coating thermal noise (CTN) limits the sensitivity of current interferometric gravitational wave detectors in the central frequency band (the region of highest sensitivity). The current mirror coating technology of ion beam sputtered (IBS) amorphous oxides, which is used on all current gravitational wave detectors has, over the past 15 years, seen only modest gains in reducing the elastic loss that generates CTN. Fortunately, crystalline GaAs/AlGaAs coatings (hereafter AlGaAs coatings) meet LIGO’s stringent optical requirements and have a CTN estimated to be 10 times lower than the current Advanced LIGO coatings. This gain in sensitivity will generate a dramatic jump in event rate, which increases as the cube of the sensitivity range. It will also allow nearby events to be observed with very high signal-to-noise ratio, which may provide insights into the structure of neutron stars and additional tests of general relativity. Finally, crystalline coatings exceed the requirements for all planned future gravitational wave detectors. Thus, this award funds an advancement in instrumentation that will benefit the field for decades. However, challenges remain as AlGaAs coatings are birefringent, experience crystal defects, and have only been made in small diameters. This award will fund the LOCCCI instrument that will enable the development of low-noise, large-diameter, crystalline coatings for gravitational wave detectors. The LOCCCI instrument will be initially used to test these coatings at large diameters (20 cm) for birefringence noise, crystal defect densities, and surface uniformity. This investigation will then inform manufacturing improvements and ultimately justify the development of the 30 cm coatings that will be deployed in the detectors. This instrument will also test that the production coatings conform to design specifications.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.