Modulation type laser interference method and device for measuring air refractive index

Abstract

The invention discloses a modulation type laser interference method and device for measuring an air refractive index. The method includes the steps that a dual-frequency laser outputs orthogonal linearly polarized lights with wavelengths of lambada 1 and lambada 2 respectively, the lights are emitted to a michelson interferometer formed by a spectroscope, a referential cube-corner prism and a measuring cube-corner prism, and respective interference signals are formed and received by two detectors after light split of the spectroscope and a polarizing beam splitter; and a quartz vacuum cavity is placed in a measuring optical path and is parallel with the light transmission direction, a synthetic wavelength is measured through moving the referential cube-corner prism to detect the phase difference change 2 pi of the interference signals of lambada 1 and lambada 2, motion of the measuring cube-corner prism is modulated through moving a piezoelectric ceramic driver, phase differences delta phi 1 and delta phi 2 of the interference signals of lambada 1 and lambada 2 when the quartz vacuum cavity is pumped into vacuum and when air is introduced in are measured, and the air refractive index n can be measured according to the length of the vacuum cavity L, the synthetic wavelength lambada S, and the phase difference variation (delta phi 2-delta phi 1). The method and the device have the advantages that the measuring accuracy reaches above 10<-9>, the environmental disturbance resistant capacity is high, and the like, and can be applied to the technical fields of precision measurement, laser interferometers, and the like.

Description

technical field [0001] The invention relates to a method and a device for measuring the refractive index of air, in particular to a method and a device for measuring the refractive index of air with modulated laser interference. Background technique [0002] Air refractive index measurement accuracy is an important factor that restricts the improvement of the accuracy of various optical measurement methods that use laser wavelength as the length reference. Air refractive index measurement methods are generally divided into two categories: indirect measurement and direct measurement. The indirect measurement method is to first measure the pressure, temperature and relative humidity of the air, and then use the Edlen formula to calculate the refractive index of the air. The measurement accuracy of this method is not better than 3×10 -8 . The direct measurement method is realized by interferometry, such as Rayleigh interferometry, French-Peru interferometry and multi-waveleng...

AI Technical Summary

Problems solved by technology

Based on the interferometric method to measure the refractive index of air, the measurement accuracy depends on the subdivision coefficient of the interference fringe and the vacuum and the air optical path length L. During the measurement, during the vacuum chamber pumping or deflation process, the air flow in the chamber changes too fast and is not uniform , will cause the interference fringes to jitter and limit the measurement accuracy. Therefore, most of the air refractive index measurement accuracy based on interferometry can only reach 10 -8

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