Novel Method to Measure the Gravitational Constant

我成功地建立了一台激光多普勒干涉仪，与高速采样示波器相连，可以测量皮米范围(&lt；10^-12米)以下1~5 kHz的振荡幅度。建造这种仪器的第一次尝试明显落后于极化稳定性，因为即使在最大采样率为5 MHz的情况下，测量的地面噪声也不能降到1 pm/hz^(1/2)以下。最后一次测量的地面噪声现在是0.13 PM/Hz^(1/2)。该仪器在偏振稳定性方面经历了升级，其形式为Glan-Taylor棱镜，现在位于重新组合分束器一侧的波片和激光输入端的法拉第隔离器之前。此外，已经注意通过使用偏振保持光纤来确保参考光束路径和信号光束路径的光路长度相等。这增加了两束光束的相干性，从而也增加了探测器处观察到的条纹的对比度。所进行的研究的一个次要方面是确保即使在皮度计以下的振荡幅度下也能使用压电测试芯片。这对于保持较低的动态对比度和较高的测量分辨率非常重要。测试结果清楚地证明了测试芯片的性能。

I succeeded to build a laser Doppler-interferometer, connected to a high-speed sampling oscilloscope, with which oscillation-amplitudes at 1~5kHz below picometer-ranges (<10^-12 m) could be measured. The first attempt of building such an instrument lagged clearly in polarization stability as the measured ground noise could not be lowered below 1pm/Hz^(1/2) even with a maximum sampling rate of 5MHz. The last measured ground noise is now at 0.13pm/Hz^(1/2).The instrument has experienced upgrades regarding the polarization stability in the form of Glan-Taylor prisms which are now in front of the waveplates on the recombining beam-splitter side and a Faraday isolator at the laser-input. Furthermore, care has been taken to ensure an equal optical path length for both the reference and the signal beam path by using polarization maintaining fibers. This increased the coherence of both beams and thus also the contrast of the observed fringes at the detectors.One minor aspect of the conducted research was to ensure the usability of the Piezo-test chip even for oszillation amplitudes below a picometer. This is important to keep the dynamic constrast low and thus the resolution of the measurements high. The results clearly proof the capability of the test-chip.