Thermal Coating Noise at Low Temperatures and Low Loss Faraday Isolators

LIGO天文台的建造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，在更高的频率下，还受到散粒噪声的限制，经典场的统计特性。涂层热噪声是由组成反射镜表面介质涂层的原子的布朗运动引起的。我们将在快速周转试验台上测量Advanced 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Advanced LIGO频段内束流大小和温度的函数，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，人们都知道非经典光场，即压缩光，原则上可以用来降低散粒噪声。这种改进受到非经典场源、压缩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，即用于注入激光的光定向耦合器。我们将开发低损耗的法拉第隔离器，以降低损耗，并扩大先进的LIGO和其他干涉引力波探测器的射程。这些改进，加上LIGO科学合作的其他人所做的改进，将有助于提高高级LIGO信号的探测率和保真度，以进一步改善对这些天体物理信号的理解。高级LIGO是有史以来建立的最复杂的实验之一。它继续将许多技术推向根本极限，满足这些极限使美国公司获得必要的优势，以保持领先地位并在世界市场上竞争。美国的光学行业在LIGO的推动下不断改进他们的镀膜，领先的商业镀膜公司都在美国。此外，具有极低热膜噪声的高质量光学涂层的开发还在时间和频率标准等其他领域产生了副产品，这使得GPS和精密计量的潜在改进成为可能。精密计量带来了精密制造的改进和世界市场份额的增加。低损耗光学元件，如我们将开发的低损耗法拉第隔离器，具有商业潜力，并在未来光信息技术、量子计算、激光物理等领域的许多科学实验中需要。Advanced LIGO在灵敏度方面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，使宇宙中能量最高的事件变得可见，并吸引新的思维进入天文学和天体物理学以及整个科学。

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.