DISPERSION INTERFEROMETER, AND METHOD OF MEASURING PHYSICAL QUANTITY OF MEASURING OBJECT

摘要

PROBLEM TO BE SOLVED: To provide a dispersion interferometer usable for actual time control, and capable of removing an influence of a high-frequency noise, reducing a measurement error caused by signal intensity change, and heightening accuracy, by extracting a phase from a signal intensity ratio of a fundamental wave and a double harmonic which are Fourier components of a modulated signal. Ž

SOLUTION: A nonlinear crystal element 10 of this dispersion interferometer changes a part of laser light (fundamental wave W1) into a double harmonic W2. A photoelastic element 12 generates phase modulation in the fundamental wave W1 as much as a modulated angle frequency ωmportion. A nonlinear crystal element 14 changes the fundamental wave W1 transmitted through plasma 30 into the double harmonic W2. A wavelength selection filter 16 allows selectively transmission of the double harmonic W2. The interferometer determines an intensity ratio between a fundamental wave component of the modulated angle frequency ωmand a double harmonic component in an interference signal, and calculates a line average electron density which is a physical quantity of the plasma 30 based on the intensity ratio and a phase variation. Ž

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