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，在更高的频率下，还会受到散粒噪声和经典场的统计特性的限制。膜层热噪声是由反射镜表面介质膜层中原子的布朗运动引起的。我们将测量先进LIGO涂层，其他介电涂层和新开发的晶体涂层的涂层热噪声，作为光束尺寸和温度的函数，在整个先进LIGO频率范围内，在一个快速回转测试平台上表征这些涂层，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，原则上可以用来减少散粒噪声。这些改进受到非经典场源、挤压器和主干涉仪之间的光学损耗的限制。主要的损耗机制之一是法拉第隔离器中的光学损耗;法拉第隔离器是用于注入激光的光学定向耦合器。我们将开发低损耗的法拉第隔离器，以减少损失，提高先进的LIGO和其他干涉引力波探测器的范围。这些改进，加上LIGO科学合作组织中其他人所做的改进，将有助于提高高级LIGO信号的探测率和保真度，以进一步提高对这些天体物理信号的理解。高级LIGO是有史以来最复杂的实验之一。它继续将许多技术推向其基本极限，满足这些极限使美国公司拥有必要的优势，以保持其领先地位并在世界市场上竞争。美国的光学行业受到LIGO的推动，不断改进其涂层，领先的商业涂层公司都在美国。此外，具有非常低的热涂层噪声的高质量光学涂层的开发在其他领域具有副产品，如时间和频率标准，这使得GPS和精密计量学的潜在改进成为可能。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，在未来的光信息技术、量子计算、激光物理等领域的许多科学实验中都需要。先进LIGO灵敏度的潜在改进将使可探测到的引力波源的数量增加至少一个数量级，使宇宙中最具能量的事件可见，并吸引新的思想进入天文学和天体物理学以及一般科学。

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.