Chen Qianghua, Luo Huifu, Wang Sumei, Wang Feng, Chen Xinhua
Key Laboratory of Advanced Machining Fundamental Science, School of Mechanical Engineering, Beijing Institute of Technology, Teaching Building 1, 5 South Zhongguancun Street, Haidian District, Beijing 100081, China.
Appl Opt. 2012 Sep 1;51(25):6106-10. doi: 10.1364/AO.51.006106.
A measurement method based on interferometry with two different reference cavity lengths is presented and applied in air refractive index measurement in which the two cavity lengths and a laser wavelength are combined to generate two wavelength equivalents of cavity. Corresponding calculation equations are derived, and the optical path configuration is designed, which is inspired by the traditional synthetic wavelength method. Theoretical analyses indicate that the measurement uncertainty of the determined index of refraction is about 2.3×10(-8), which is mainly affected by the length precision of the long vacuum cavity and the ellipticity of polarization components of the dual-frequency laser, and the range of nonambiguity is 3.0×10(-5), which is decided by the length difference of the two cavities. Experiment results show that the accuracy of air refractive index measurement is better than 5.0×10(-8) when the laboratory conditions changes slowly. The merit of the presented method is that the classical refractometry can be also used without evacuation of the gas cavity during the experiment. Furthermore, the application of the traditional synthetic wavelength method may be extended by using the wavelength equivalents of cavity, any value of which can be easily acquired by changing cavity length rather than using actual wavelengths whose number is limited.
提出了一种基于干涉测量法的测量方法，该方法采用两种不同的参考腔长度，并应用于空气折射率测量中，其中将两种腔长度与激光波长相结合，以生成腔的两个波长等效值。推导了相应的计算方程，并设计了光路配置，其灵感来源于传统的合成波长法。理论分析表明，所确定折射率的测量不确定度约为2.3×10(-8)，主要受长真空腔的长度精度和双频激光偏振分量的椭圆率影响，无模糊范围为3.0×10(-5)，由两个腔的长度差决定。实验结果表明，当实验室条件缓慢变化时，空气折射率测量的精度优于5.0×10(-8)。该方法的优点是在实验过程中不排空气体腔也可使用经典折射计。此外，通过使用腔的波长等效值，可以扩展传统合成波长法的应用，通过改变腔长度可以轻松获得其任何值，而不是使用数量有限的实际波长。
