Refractive-index determination of solids from first- and second-order critical diffraction angles of periodic surface patterns

Christoph Meichner,Andreas E Schedl,Lothar Kador,Hans-Werner Schmidt,Klaus Kreger,Christian Neuber

doi:10.1063/1.4928654

Abstract

Highlights

The precise knowledge of the refractive-index dispersion of solid materials is required for numerous applications such as thin-film coatings, fiber optics, optical elements, and many more.[1,2] new methods for its determination are still being devised today,[3] many of which are optimized for a particular type of application
We demonstrate the methods on a polydimethylsiloxane film (Sylgard® 184) and compare our data to those obtained with a standard Abbe refractometer at several wavelengths between 489 and 688 nm
The data obtained from Eq (2) become slightly larger when the grating period Λ determined from the parameters of the holographic inscription is replaced by Λ = 999.7 ± 1.0 nm, the average of the Λ values calculated from Eq (3)

Summary

INTRODUCTION

The precise knowledge of the refractive-index dispersion of solid materials is required for numerous applications such as thin-film coatings, fiber optics, optical elements, and many more.[1,2] new methods for its determination are still being devised today,[3] many of which are optimized for a particular type of application. Spectral ellipsometry is an alternative method for investigating thin solid films This technique is more elaborate and the accuracy of the results depends strongly on the model used to evaluate the experimental data. Holographic exposure of many azobenzene derivatives gives rise to photo-induced mass transport over macroscopic distances, which results in the formation of surface relief gratings (SRGs).[6,7] the applicability of our method is not limited to photo-active systems because it only requires the periodic pattern. We demonstrate this for a transparent colorless polydimethylsiloxane (PDMS) working stamp. The surface pattern was generated by imprinting a SRG, which was holographically fabricated on an azobenzene glass

THEORY

EXPERIMENTAL

DISCUSSION

CONCLUSION