Angle-resolved spectral Fabry–Pérot interferometer for single-shot measurement of refractive index dispersion over a broadband spectrum

Abstract

An angle-resolved spectral Fabry–Pérot interferometer is reported for fast and accurate measurement of the refractive index dispersion of optical materials with parallel plate shape. The light sheet from the wavelength tunable laser is incident on the parallel plate with converging angles. The transmitted interference light for each angle is dispersed and captured by a 2D sensor, in which the rows and the columns are used to simultaneously record the intensities as a function of wavelength and incident angle, respectively. The interferogram, named angle-resolved spectral intensity distribution, is analyzed by fitting the phase information instead of finding the fringe peak locations that present periodic ambiguity. The refractive index dispersion and the physical thickness can be then retrieved from a single-shot interferogram within 18 s. Experimental results of an optical substrate standard indicate that the accuracy of the refractive index dispersion is less than 2.5 × 10−5 and the relative uncertainty of the thickness is 6 × 10−5 mm (3σ) due to the high stability and the single-shot measurement of the proposed system.