CAREER: Integrated Research and Education on Gravitational Wave Detector Optics

这项职业资助支持光学研究工作，以提高引力波探测器和其他精密光学测量的灵敏度，并利用光学专业知识为华盛顿特区的高中生组织和举办为期一天的有趣比赛——光学奥林匹克竞赛。引力波来自爱因斯坦的引力理论，是爱因斯坦理论中为数不多的可以通过实验与其他引力理论（如艾萨克·牛顿的理论）进行检验的具体预测之一。确定爱因斯坦、牛顿或其他引力理论是否正确地描述了我们的宇宙，对于全面理解自然规律是必要的。这个实验是由激光干涉仪引力波天文台（LIGO）在路易斯安那州和华盛顿州用两个4公里长的大型探测器进行的。一旦引力波被LIGO探测到，这些探测将成为研究宇宙的另一种方法，与光学、无线电和其他传统望远镜互补，但又不同。通过引力波探测，我们希望了解更多关于黑洞、中子星、超新星、宇宙起源和其他高能天文事件的信息。不幸的是，引力波对LIGO探测器的影响非常小，其他现象产生的噪声很容易淹没引力波信号。这项拨款支持更好地理解和减少涂层热噪声的工作，这是限制我们探测引力波能力的关键噪声源。相关的教育和推广项目是通过一个有趣和有教育意义的光学奥林匹克竞赛，将我们在LIGO工作中开发的光学的兴奋传递给高中生。除了个人和团队在光学知识和理解方面的竞争之外，还将有小组讨论、客座讲师和参观美国大学的科学实验室。根据涨落耗散定理，激光干涉引力波光学涂层中的热噪声是由机械损耗引起的。我们将通过开发用于LIGO涂层的砷化铝镓（AlGaAs）晶体和氮化硅来降低这种热噪声。在不同条件下的其他精密光学实验中，AlGaAs已经显示出较低的热噪声。在LIGO条件下使用AlGaAs的初步结果表明，与现有涂层相比，机械损耗有所改善，但不如预期的那么大。这可能是由于基材上的表面条件，这将探索使用各种化学和机械表面处理。这些处理对AlGaAs机械损耗的影响将使用正常模式质量因子或Q测量来探索。我们还将更好地表征和理解来自AlGaAs的热噪声，使用完整的机械损失描述作为刚度张量的虚数部分。这可能允许通过涂层的层设计来改善热噪声的方法，而不是使用更好的材料进行改进。光学奥林匹克竞赛将包括一个形成性评估，以确定奥林匹克竞赛的哪些元素有助于提高学生对物理和光学的理解，并改善他们对STEM职业的印象。本次评估和奥林匹克竞赛的总体结果将以期刊文章或会议报告的形式提交给物理教育研究界。

This CAREER grant supports work on optics research to improve the sensitivity of gravitational wave detectors and other precision optical measurements as well as using expertise in optics to organize and host a day of fun competition, the Optics Olympiad, for Washington DC high school students. Gravitational waves come from Einstein's theory of gravity, and are one of the few specific predictions of Einstein's theory that can be experimentally checked against other theories of gravity (like Isaac Newton's). Determining if Einstein's, Newton's, or perhaps some other theory of gravity correctly describes our universe is necessary to developing a complete understanding of the laws of nature. This experiment is being performed by the Laser Interferometer Gravitational-wave Observatory (LIGO) with two large, four kilometer long detectors in Louisiana and Washington state. Once gravitational waves are detected by LIGO, these detections will serve as another method of studying the universe, complementary but different from optical, radio, and other conventional telescopes. With gravitational wave detections, we expect to learn more about black holes, neutron stars, supernova, the origins of the universe, and other high energy astronomical events. Unfortunately, the effect of gravitational waves on the LIGO detectors is very small, and noise from other phenomenon can easily overwhelm the gravitational signal. This grant supports work to better understand and reduce coating thermal noise, a critical noise source that limits our ability to detect gravitational waves. The related education and outreach project is to pass on the excitement about optics we develop working on LIGO to high school students through a fun and educational competition, the Optics Olympiad. In addition to individuals and teams competing on knowledge and understanding of optics, there will be panel discussions, a guest lecturer, and tours of science laboratories at American University.Thermal noise in the coatings of the LIGO optics is caused by mechanical loss, as shown by the Fluctuation Dissipation theorem. We will reduce this thermal noise by developing Aluminum-Gallium-Arsenide (AlGaAs) crystals and silicon nitride for use as LIGO coatings. AlGaAs has already shown lower thermal noise in other precision optics experiments under different conditions. Preliminary results with AlGaAs under LIGO conditions indicate some improvement in mechanical loss compared to current coatings, but not as much as expected. This may be due to surface conditions on the substrate, which will be explored using various chemical and mechanical surface treatments. The effects of these treatments on AlGaAs mechanical loss will be explored using normal mode quality factor, or Q, measurements. We will also better characterize and understand thermal noise from AlGaAs using the complete description of mechanical loss as the imaginary part of the stiffness tensor. This may allow for ways to improve thermal noise through the layer design of the coating beyond improvements from better materials. The Optic Olympiad will include a formative assessment to determine what elements of the Olympiad are helping to reach the goals of increasing students understanding of physics and optics as well as improving their impression of STEM careers. Results of this assessment and the Olympiad in general will be presented to the physics education research community, likely as a journal article or conference presentation.