METHOD AND INSTRUMENT FOR MEASURING COMPLEX INDEX OF REFRACTION

摘要

PURPOSE: To highly sensitively measure the variation of a refractive index at an arbitrary wavelength without noise by providing an electrooptic phase modulator, Mach- Zehnder interferometer, wave length plates, polarization beam splitters, and photoreceptor elements. ;CONSTITUTION: The title instrument is constituted mainly of an electrooptic phase modulator 2 polarization beam splitters 3-8 sample 9 to be measured, wavelength plates 16-18, and photoreceptor elements 19-26. The angles of the elements 19-26 are set and the expressions of the modulated signal components of two frequency components are finally obtained by aiming at the frequency components only. When the ratio between the signals is taken by performing lock-in detection, phase variation can be measured with extremely high sensitivity without receiving any disturbance from noise existing in the instrument and gain variation. This analysis is performed after making signal components of various kinds of frequencies generated when different kinds of frequency modulation is performed on a modulator 2 and a signal to be measured passes through the wavelength plates 16-18. Therefore, the variation of a refractive index at an arbitrary wavelength and a gain change which occurs in the sample 9 can be measured simultaneously but separately.;COPYRIGHT: (C)1994,JPO&Japio