Fu Haijin, Wang Yue, Hu Pengcheng, Tan Jiubin, Fan Zhigang
Institute of Ultra-Precision Optoelectronic Instrument Engineering, Harbin Institute of Technology, Harbin 150001, China.
Postdoctoral Research Station of Optical Engineering, Harbin Institute of Technology, Harbin 150001, China.
Sensors (Basel). 2018 Mar 2;18(3):758. doi: 10.3390/s18030758.
Even after the Heydemann correction, residual nonlinear errors, ranging from hundreds of picometers to several nanometers, are still found in heterodyne laser interferometers. This is a crucial factor impeding the realization of picometer level metrology, but its source and mechanism have barely been investigated. To study this problem, a novel nonlinear model based on optical mixing and coupling with ghost reflection is proposed and then verified by experiments. After intense investigation of this new model's influence, results indicate that new additional high-order and negative-order nonlinear harmonics, arising from ghost reflection and its coupling with optical mixing, have only a negligible contribution to the overall nonlinear error. In real applications, any effect on the Lissajous trajectory might be invisible due to the small ghost reflectance. However, even a tiny ghost reflection can significantly worsen the effectiveness of the Heydemann correction, or even make this correction completely ineffective, i.e., compensation makes the error larger rather than smaller. Moreover, the residual nonlinear error after correction is dominated only by ghost reflectance.
即使经过海德曼校正后，外差激光干涉仪中仍存在残留的非线性误差，范围从数百皮米到几纳米。这是阻碍实现皮米级计量的关键因素，但其来源和机制几乎未得到研究。为研究此问题，提出了一种基于光学混频和与鬼反射耦合的新型非线性模型，随后通过实验进行了验证。在深入研究该新模型的影响后，结果表明，由鬼反射及其与光学混频的耦合产生的新的附加高阶和负阶非线性谐波对整体非线性误差的贡献可忽略不计。在实际应用中，由于鬼反射率较小，对李萨如图形轨迹的任何影响可能都不可见。然而，即使是微小的鬼反射也会显著恶化海德曼校正的效果，甚至使该校正完全无效，即补偿使误差增大而非减小。此外，校正后的残留非线性误差仅由鬼反射率主导。
