Thermal Coating Noise at Low Temperatures and Low Loss Faraday Isolators

LIGO天文台的建立是为了探测来自许多不同天体物理源的引力波，如中子星和黑洞双星系统或超新星爆炸。在目前正在进行的升级之后，探测器将受到涂层热噪声的限制，并且在更高的频率下，受到经典场统计特性的射击噪声的限制。涂层热噪声是由构成镜面上介电涂层的原子的布朗运动引起的。我们将在一个快速旋转试验台上测量先进LIGO涂层、其他介质涂层和新开发的晶体涂层的涂层热噪声，作为整个先进LIGO频段上光束尺寸和温度的函数，以表征这些涂层并验证用于描述它们的理论模型。近30年来，人们已经知道，非经典光场，即压缩光，原则上可以用来降低射击噪声。这种改进受到非经典场源、挤压器和主干涉仪之间的光损耗的限制。主要损耗机制之一是法拉第隔离体中的光损耗；一种用于注入激光的光学定向耦合器。我们将开发低损耗法拉第隔离器，以减少损耗，提高先进LIGO和其他干涉引力波探测器的探测范围。这些改进，连同LIGO科学合作组织其他成员所做的改进，将有助于提高高级LIGO信号的检出率和保真度，从而进一步提高对这些天体物理信号的理解。先进的LIGO是有史以来最复杂的实验之一。它继续推动许多技术达到其基本极限，满足这些极限为美国公司提供了保持领先地位和在世界市场竞争所需的优势。美国的光学行业在LIGO的推动下不断改进他们的涂层，领先的商业涂层公司都在美国。此外，开发具有非常低热涂层噪声的高质量光学涂层在时间和频率标准等其他领域也有衍生产品，这可能会改善GPS和精密计量。精密计量导致精密制造的改进和世界市场份额的增加。我们将开发的低损耗法拉第隔离器等低损耗光学元件具有商业潜力，并且在光学信息技术，量子计算，激光物理等领域的许多未来科学实验中都需要。先进的LIGO在灵敏度上的潜在改进将使可探测到的引力波源的数量至少增加一个数量级，使宇宙中最具能量的事件变得可见，并吸引天文学和天体物理学以及一般科学的新思想。

The LIGO observatories were built to detect gravitational waves from many different astrophysical sources such as neutron star and black hole binary systems or supernova explosions. In the wake of the currently ongoing upgrade, the detectors will be limited by coating thermal noise and, at higher frequencies, by shot noise, the statistical properties of classical fields. Coating thermal noise is caused by the Brownian motion of the atoms which comprise the dielectric coatings on the surfaces of the mirrors. We will measure coating thermal noise of the Advanced LIGO coatings, other dielectric coatings, and of newly developed crystalline coatings as a function of beam size and temperature over the entire Advanced LIGO frequency band in a fast turn-around testbed to characterize these coating and verify the theoretical models used to describe them. It is known for almost 30 years that non-classical light fields, squeezed light, can in principle be used to reduce shot noise. The improvements are limited by optical losses between the source of the non-classical field, the squeezer, and the main interferometer. One of the dominating loss mechanisms are optical losses in the Faraday isolator; an optical directional coupler for the injected laser light. We will develop low loss Faraday isolators to reduce the losses and improve the range of Advanced LIGO and other interferometric gravitational wave detectors. These improvements, together with improvements made by others in the LIGO Science Collaboration, will help to increase the detection rate and fidelity of the Advanced LIGO signals to further improve the understanding of these astrophysics signals.Advanced LIGO is one of the most complex experiments ever built. It continues to push many technologies to its fundamental limits and meeting these limits gives US companies the needed edge to maintain their lead and compete in the world markets. The optical industry in the US was pushed by LIGO to continuously improve their coatings and the leading commercial coating companies are all in the US. In addition, the development of high quality optical coatings with very low thermal coating noise has spin-offs in other areas like time and frequency standards which enable potential improvements in GPS and in precision metrology. Precision metrology leads to improvements in precision manufacturing and increased shares of world markets. Low loss optical components such as the low loss Faraday isolator we will develop have commercial potential and are required in many future scientific experiments in optical information technology, quantum computing, laser physics, and other areas. The potential improvements in the sensitivity of Advanced LIGO will increase the number of detectable gravitational wave sources by at least an order of magnitude, making visible the most energetic events in the Universe and attracting new minds to astronomy and astrophysics and to science in general.