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Measurement of air refractive index fluctuation based on interferometry with two different reference cavity lengths
Qianghua Chen1, Huifu Luo, Sumei Wang
1Key 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. chenqianghua@tsinghua.org.cn
Applied Optics
|September 5, 2012
Summary
A novel interferometry method uses two reference cavity lengths for precise air refractive index measurement. This technique offers high accuracy and extends the synthetic wavelength method
Area of Science:
- Metrology
- Optical Physics
- Interferometry
Background:
- Accurate measurement of the air refractive index is crucial for various scientific and industrial applications.
- Traditional methods for refractive index measurement often require vacuum conditions or have limitations in precision and range.
Purpose of the Study:
- To present a new interferometric measurement method for determining the air refractive index.
- To enhance the synthetic wavelength method by introducing tunable "wavelength equivalents of cavity."
Main Methods:
- Utilizing interferometry with two distinct reference cavity lengths.
- Combining cavity lengths and laser wavelength to generate two "wavelength equivalents of cavity."
- Deriving calculation equations and designing an optical path configuration inspired by the synthetic wavelength method.
Main Results:
- Theoretical analysis predicts a measurement uncertainty of approximately 2.3×10⁻⁸ for the refractive index.
- The non-ambiguity range is determined to be 3.0×10⁻⁵, dependent on the cavity length difference.
- Experimental results demonstrate an air refractive index measurement accuracy better than 5.0×10⁻⁸ under stable laboratory conditions.
Conclusions:
- The presented method achieves high accuracy in air refractive index measurement without requiring gas evacuation.
- The technique extends the applicability of the synthetic wavelength method by enabling flexible acquisition of "wavelength equivalents of cavity."
- This approach offers a valuable advancement for refractometry and related optical measurements.
