GEO600引力波干涉仪分束器中的热折射和热化学噪声
Thermo-refractive and thermo-chemical noise in the beamsplitter of GEO600 gravitational-wave interferometer
摘要：
Braginsky、Gorodetsky和Vyatchanin已经证明，热折射涨落是干涉引力波探测器中噪声的重要来源。特别是，在GEO600分束器的热折射噪声预计将作出重大贡献的干涉仪的总噪声预算。在这里，我们提出了一个新的计算的GEO600热折射噪声，考虑到光束的椭圆形的轮廓，更重要的是，激光束在分束器中诱导一个驻波电磁波的事实。与先前的估计相比，使用更新的参数导致在GEO600频带的低频部分中计算出的噪声幅度的总体减小约5倍。我们还发现，与以前的计算相比，热折射波动导致白噪声在600 Hz和39 MHz之间，在$8.5\cdot 10^{-24}$ Hz $^{-1/2}$的水平。最后，我们描述了一种新型的热噪声，我们称之为热化学噪声。这是由光学活性化学杂质或结构缺陷沿驻波陡峭强度梯度方向的随机运动引起的。我们讨论了潜在的相关性的热化学噪声GEO600。
英文摘要：
Braginsky, Gorodetsky, and Vyatchanin have shown that thermo-refractive fluctuations are an important source of noise in interferometric gravitational-wave detectors. In particular, the thermo-refractive noise in the GEO600 beamsplitter is expected to make a substantial contribution to the interferometer's total noise budget. Here we present a new computation of the GEO600 thermo-refractive noise which takes into account the beam's elliptical profile and, more importantly, the fact that the laser beam induces a standing electromagnetic wave in the beamsplitter. The use of updated parameters results in the overall reduction of the calculated noise amplitude by a factor of about 5 in the low-frequency part of the GEO600 band, compared to the previous estimates. We also find, by contrast with previous calculations, that thermo-refractive fluctuations result in white noise between 600 Hz and 39 MHz, at a level of $8.5\cdot 10^{-24}$Hz$^{-1/2}$. Finally, we describe a new type of thermal noise, which we call the thermo-chemical noise. This is caused by a random motion of optically-active chemical impurities or structural defects in the direction along a steep intensity gradient of the standing wave. We discuss the potential relevance of the thermo-chemical noise for GEO600.
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