Optical Path and Birefringence Characterization of Crystalline Coatings for Gravitational-wave Detectors

该奖项支持对砷化铝镓(AlGaAs)晶镜的热性能和光学性能的研究。晶镜是一种非常薄的(微米级)单晶涂层，覆盖在合适的衬底上，例如熔融石英玻璃。这些结晶涂层有可能显著降低干涉型引力波探测器中的噪声，如激光干涉仪引力波天文台(LIGO)操作的那些。先进的LIGO探测器开创了引力波天文学领域的先河，在过去五年中进行了数十次探测。为了扩大探测器的天体物理覆盖范围，近期和未来的升级都在计划之中。根据该奖项开展的工作支持这些升级。它还通过培训未来的科学家支持间接的科学发展，并包含一个重要的面向高中生和老年人的外联部分。目前可用的镜面涂层中的涂层热噪声(CTN)现在限制了我们增加升级的探测器的天体物理覆盖范围的能力。晶态AlGaAs涂层有可能解决这一问题，因为它们可以将CTN降低至少5倍。然而，要实现适合于干涉型引力波探测器的AlGaAs涂层，还需要做大量的工作。大部分的研究都是为了表征AlGaAs薄膜的双折射、薄膜上的双折射均匀性、热光效应和热光均匀性。将建造一台专门的迈克尔逊干涉仪，以绘制直径为3英寸的AlGaAs涂层全面的双折射图。此外，热光噪声的消除依赖于整个涂层的热光效应的一致性。因此，将对现有的热光设备进行改进，以将热光效应映射到整个涂层上。该提案的更广泛影响包括跨代团队参与科学研究。将启动“利用时空”项目，由至少一名老年人和一名或多名高中生组成的团队将共同努力，建造一个功能强大的5-30 MHz天线。他们将使用为无线电接收开发的免费软件工具，对其天线接收的数据进行频谱和听觉分析。这项活动“培养”他们使用相同的工具对公共引力波数据进行类似的分析。每个信号都有不同的听觉特征和光谱特征，这些特征共同给出了关于其来源的线索。团队将查找、保存和分类此类事件和功能。他们在一个专门的Slack工作区上讨论了他们的发现。这些团队将在恩布里-里德尔航空大学的演讲中报告他们的结果，一些团队将参加一个小型科学会议，如业余射电天文学协会的年度会议或地区性APS四角会议。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。

This award supports studies of thermal and optical properties of aluminum gallium arsenide (AlGaAs) crystalline mirrors. Crystalline mirrors are extremely thin (micrometer-scale) monocrystalline coatings laid on top of a suitable substrate such as fused silica glass. These crystalline coatings have the potential to significantly reduce the noise in interferometric gravitational wave detectors like those operated by the Laser Interferometer Gravitational-Wave Observatory, LIGO. The Advanced LIGO detectors inaugurated the field of gravitational wave astronomy with dozens of detections in the last five years. To increase the astrophysical reach of the detectors, both near-term and future upgrades are being planned. The work performed under this award supports these upgrades. It also supports indirect development of science through the training of future scientists, and contains a significant outreach component to high-school students and senior citizens.Coating thermal noise (CTN) in currently available mirror coatings now constrains our ability to increase the astrophysical reach of upgraded detectors. Crystalline AlGaAs coatings have the potential to solve this problem since they can reduce CTN by a factor of at least five. Yet, significant work needs to be done to realize an AlGaAs coating suitable for installation in interferometric gravitational wave detectors. Most of the studies are aimed at characterizing AlGaAs coating birefringence, birefringence uniformity across the coating, thermo-optic effect, and thermo-optic uniformity. A specialized Michelson interferometer will be constructed to map birefringence over the full face of 3 inch diameter AlGaAs coatings. Also, thermo-optic noise cancellation relies on uniformity of the thermo-optic effect across the coating. Existing thermo-optic apparatus will therefore be modified to map the thermo-optic effect over the full coating. The broader impacts of the proposal include the involvement of cross-generational teams in scientific inquiry. Project “Tap Into Spacetime” will be launched where teams constituted of at least one senior citizen and one or more high school students will work together to build a capable, 5-30 MHz, antenna. They will use free software tools developed for radio reception to perform spectrographic and aural analysis of the data received by their antenna. This activity "graduates" them to perform a similar analysis of public gravitational wave data using the same tools. Each signal has a distinct aural character and spectrographic signature that together give clues about its origin. The teams will find, save, and categorize such events and features. They discuss their findings on a dedicated Slack workspace. The teams will report their results with talks at Embry-Riddle Aeronautical University and some will attend a small scientific meeting such as the Society of Amateur Radio Astronomer’s annual meeting or the regional APS four-corners meeting.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.