Refractive index determination by coherence scanning interferometry

Abstract

Coherence scanning interferometry is established as a powerful noncontact, three-dimensional, metrology technique used to determine accurate surface roughness and topography measurements with subnanometer precision. The helical complex field (HCF) function is a topographically defined helix modulated by the electrical field reflectance, originally developed for the measurement of thin films. An approach to extend the capability of the HCF function to determine the spectral refractive index of a substrate or absorbing film has recently been proposed. In this paper, we confirm this new capability, demonstrating it on surfaces of silicon, gold, and a gold/palladium alloy using silica and zirconia oxide thin films. These refractive index dispersion measurements show good agreement with those obtained by spectroscopic ellipsometry.

Measurement of thin film interfacial surface roughness by coherence scanning interferometry

“…The development of the HCF function has already extended its capability for the determination of refractive index. 23 This paper extends its capability further to include the threedimensional measurement of buried interfaces. 11.…”

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

“…Angle-resolved spectral Fabry-Pérot interferometer for single-shot measurement of refractive index dispersion over a broadband spectrum emitted from different light sources. Some of the interfero metric methods [7,[9][10][11] can measure the absolute refractive index over a wide wavelength region and the thickness of the sample simultaneously. However, the rotation of the sample is needed to increase the effective optical path length such that the number of fringes sweeping past the photodetector can be counted.…”

“…Refractive index dispersion is an essential material param eter in various optical applications such as femtosecond pulse lasers, broadband optical communications and nonlinear optics. A variety of refractive index measurement technologies have been developed such as the ellipsometric method [1], the prism coupling method [2], the minimum deviation method [3], the Abbé refractometer [4], the laser feedback method [5] and interferometrybased methods [6][7][8][9][10][11][12][13][14][15][16]. Ellipsometry is ideal for the refractive index measurement of thin films and bulk samples near resonance frequencies.…”

“…The interferometrybased methods are usually employed for detecting a very small relative phase difference, which could be extended to measuring the absolute refractive index, such as Michelson [6][7][8][9][10], Mach-Zehnder [11], Fabry-Pérot [12][13][14], lateral shearing [15] and selfmixing [16] inter ferometric technologies. Most of the existing methods [6,8,[12][13][14][15][16] are related to the measurement of the refractive index value at a single wavelength or several discrete wavelengths…”