Fu Haijin, Wu Guolong, Hu Pengcheng, Ji Ruidong, Tan Jiubin, Ding Xuemei
Appl Opt. 2018 Feb 20;57(6):1463-1467. doi: 10.1364/AO.57.001463.
Heterodyne interferometers suffer from thermal drift of optics (TDO), which may introduce error even up to several micrometers. In this paper, we propose a symmetric heterodyne interferometer with spatially separated beams, which realizes completely balanced optical paths between probe and reference beams and simultaneously avoids the optical mixing, and thereby is theoretically capable of eliminating TDO and the periodic nonlinearity (PNL). To validate the performance of the proposed interferometer, first a special experimental setup is constructed, with which the TDO test can be conducted in vacuum, and the result shows that a thermal coefficient of 1.2 nm/°C is achieved. Next, the PNL of the proposed interferometer is measured by both the frequency domain method and the phase quadrature method, which demonstrates an undetectable PNL at a noise level of 13 pm.
外差干涉仪存在光学热漂移（TDO）问题，这可能会引入高达几微米的误差。在本文中，我们提出了一种具有空间分离光束的对称外差干涉仪，它实现了探测光束和参考光束之间完全平衡的光路，同时避免了光学混频，从而在理论上能够消除TDO和周期性非线性（PNL）。为了验证所提出干涉仪的性能，首先构建了一个特殊的实验装置，利用该装置可以在真空中进行TDO测试，结果表明实现了1.2 nm/°C的热系数。接下来，通过频域法和相位正交法测量了所提出干涉仪的PNL，结果表明在13 pm的噪声水平下PNL不可检测。
