REFRACTIVE INDEX VARIATION MEASUREMENT INSTRUMENT AND METHOD

摘要

PROBLEM TO BE SOLVED: To provide an instrument and a method for measuring an absolute value of a refractive index variation generated when applying an external field to optical crystal by measuring interference fringes in a Mach-Zehnder interferometer at a plurality of wavelengths.SOLUTION: A refractive index variation measurement instrument and a method by using the same, for measuring a refractive index variation when applying an external field to a specimen comprises: a laser which oscillates coherent light having a plurality of wavelengths; an interferometer which branches the coherent light into reference light and test light and multiplexes transmitted test light to generate interference fringes; measurement means which observes the interference fringes to measure phase differences between the reference light and the test light; and computation means which computes an absolute value of the refractive index variation on the basis of wavelengths of the coherent light and phase differences measured at the wavelengths of the coherent light. The absolute value of the refractive index variation is computed as |Δn(f)|=|Δn| by computing D=2π×(-Δn(F) L) where a gradient of a line obtained by plotting the phase differences per reciprocal of wavelengths is denoted as D and a length in an optical path direction of the specimen is denoted as L.