RUI: Advancing Gravitational-Wave Optics to Further Explore the Cosmos

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。阿尔伯特·爱因斯坦在1916年预言引力波是广义相对论的结果。一个世纪后，美国国家科学基金会资助的激光干涉引力波天文台（LIGO）通过观测合并黑洞产生的引力波，打开了一扇了解宇宙的新窗口。此后，LIGO及其国际合作伙伴Virgo和Kagra已经探测到来自近100个星系的引力波。通过高级LIGO+ (A+)升级和潜在的低温硅探测器旅行者（Voyager），扩大LIGO的覆盖范围的工作正在进行中。美国下一代天文台“宇宙探索者”也在开发中。这些探测器将使用光学技术深入观察宇宙的阴暗面，为新奇和未知的事物打开广阔的发现之门。该项目将吸引加州州立大学富勒顿分校（CSUF）的学生和教师参与实验研究，旨在推进光学技术，进一步利用引力波探索宇宙。学生和PI将表征和开发技术，以减少光学涂层的激光散射量。他们将测量低温下硅的光学散射，并估计其对引力波探测器性能的影响。他们将首次在旅行者号计划的波长和温度以及宇宙探索者可能的低温实现下绘制由于硅双折射引起的激光损耗图。这些研究将帮助A+将引力波观测的频率提高一倍，并帮助旅行者号和宇宙探索者号观测黑洞和中子星碰撞到第一批恒星的时代。这项工作将进一步促进光学领域的发展，并可能导致商业光学的改进。在加州大学旧金山分校进行这项研究，将对传统上在物理学领域代表性不足的群体的学生产生不成比例的积极影响。该项目将吸引加州州立大学富勒顿分校（CSUF）的学生和教师参与实验研究，旨在推进光学技术，进一步利用引力波探索宇宙。为了实现他们的目标，A+和Cosmic Explorer需要为1微米波长的激光提供室温光学涂层，这种涂层可以改善热噪声，同时具有优异的光学性能，包括光学散射。热处理（退火）可以降低涂层的热噪声和光散射。学生和PI将使用退火散射计和角度分辨散射计来表征和开发技术，以减少最有前途的涂层的散射。旅行者号的技术可以通过在低温（123 K，硅热膨胀系数的零交叉）下使用晶体硅光学器件来减少热噪声和热像差，从而扩展LIGO和宇宙探测器的探测范围。PI和学生将使用低温试验台测量高纯度晶体硅在低温下的表面、体积和涂层光学散射，并估计其对引力波探测器性能的影响。由于这些透明晶体硅光学器件的双折射造成的光学损耗也会降低未来探测器的天体物理探测范围。PI和学生们将首次利用光学腔绘制2微米波长和123 K下晶体硅的双折射图。这些研究将帮助A+将引力波观测和旅行者号以及可能的宇宙探测器的低温实现的速度提高一倍，以观测黑洞和中子星碰撞到第一颗恒星的时代。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. Albert Einstein predicted gravitational waves as a consequence of general relativity in 1916. A century later, the NSF-funded Laser Interferometer Gravitational-Wave Observatory (LIGO) opened a new window on the universe by observing gravitational waves from merging black holes. LIGO and its international partners Virgo and Kagra have since detected gravitational waves from nearly 100 systems. Work is underway to extend the reach of LIGO through the Advanced LIGO+ (A+) upgrades and a potential cryogenic silicon detector, Voyager. A next-generation US observatory, Cosmic Explorer, is also being developed. These detectors will use optical technology to peer deeply into the universe’s dark side and open a wide discovery aperture to the novel and unknown. This project will engage students and faculty at California State University, Fullerton (CSUF) in experimental research aimed at advancing optical technology to further explore the cosmos with gravitational waves. Students and the PI will characterize and develop techniques to reduce the amount of laser light scattered by optical coatings. They will measure the optical scattering of silicon at cryogenic temperatures and estimate its effects on gravitational-wave detector performance. They will map the laser light loss due to birefringence of silicon, at the wavelength and temperature planned for Voyager and possible cryogenic realizations of Cosmic Explorer, for the first time. These studies will help A+ to double the rate of gravitational-wave observations and Voyager and Cosmic Explorer to observe black hole and neutron star collisions to the era of the first stars. This work will additionally contribute to the field of optics and potentially lead to improvements in commercial optics. Conducting this research at CSUF will have a disproportionately positive impact on students from groups traditionally underrepresented in physics.This project will engage students and faculty at California State University, Fullerton (CSUF) in experimental research aimed at advancing optical technology to further explore the cosmos with gravitational waves. To achieve their goals, A+ and Cosmic Explorer require room-temperature optical coatings for 1-micron-wavelength laser light that have improved thermal noise, with still excellent optical properties, including optical scatter. Heat treatment (annealing) of coatings has been shown to decrease both their thermal noise and optical scatter. Students and the PI will employ an annealing scatterometer and an angle-resolved scatterometer to characterize and develop techniques to reduce scattering from the most promising coatings. Voyager technology could extend the reach of LIGO and Cosmic Explorer by reducing thermal noise and thermal aberrations using crystalline silicon optics operated at cryogenic temperatures (123 K, a zero crossing of silicon’s thermal expansion coefficient). The PI and students will use a cryogenic testbed to measure the surface, bulk, and coated optical scattering for high-purity crystalline silicon at cryogenic temperatures and estimate its effects on gravitational-wave detector performance. Optical losses due to birefringence in these transparent crystalline silicon optics could also decrease the astrophysical reach of future detectors. The PI and students will map the birefringence of crystalline silicon at 2-micron-wavelength and 123 K for the first time, using an optical cavity. These studies will help A+ to double the rate of gravitational-wave observations and Voyager and possible cryogenic realizations of Cosmic Explorer to observe black hole and neutron star collisions to the era of the first stars.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.