Measurement of refractive index and thickness of transparent plate by dual-wavelength interference

Abstract

We developed an accurate and efficient method for measuring the refractive indices of a transparent plate by analyzing the transmitted intensity versus angle of incidence. By using two different wavelengths, we resolved the 2pi-ambiguity inherent to the phase measurement involving a thick medium, leading to independent determination of the absolute index of refraction and the thickness with a relative uncertainty of 10(-5). The validity and the accuracy of our method were confirmed with a standard reference material. Furthermore, our method is insensitive to environmental perturbations, and simple to implement, compared to the conventional index measurement methods providing similar accuracy.

Refractive Index Determination for a Plane Dielectric Layer Using the Measurements of Transmitted Beam Intensity

“…Figure 2 demonstrates the dependences of functions f(T H ,T E ) (4) and g(T H,E ) (5) on the refractive index of a layer. The first of them is monotonic, what provides the opportunity to use that for refractive index determination as by the method of experimental calibration directly on a curve, as using analytical technique according equation (6) (the corresponding curve is also shown on Figure 2). (5), (4) and (6), on the refractive index n of a transparent dielectric layer, when its thickness h = 0.75λ and the angle of incidence φ = 30º…”

Determination of thickness uniformity of a transparent film based on in-plane ESPI and radial basis function

“…t a n Im , Re , 5 1 where Re and Im represent the real and imaginary parts of ( ) c x y , . where n 0 and n are the refractive indices in air and the transparent plate, respectively.…”

“…Variable interferometric methods have been proposed to determinate the parameters because the accuracies are not affected by the small loss in the sample. Hee Joo Choi et al developed a modified FabryPerot method which employs two lasers with considerably different wavelengths [1]. Zhi-Cheng Jian et al improved an optical technique based on the heterodyne interferometry and the twowavelength interferometry [2].…”

Determination of refractive index of transparent plate by Fabry-Perot fringe analysis

“…With this method, we could resolve the 2π-ambiguity inherent to the phase measurement in a thick medium, leading to an accurate determination of both of the absolute index of refraction and the thickness 14 . In this work, by applying the same method to a 1 mm-thick fused silica plate, we describe the details of the process of determining the index of refraction and the thickness simultaneously.…”