Direct method of extracting complex refractive index from routine Fourier transform infrared reflectance/transmittance measurements

Braden Czapla; Leonard Hanssen

doi:10.1117/12.2568502

20 August 2020 Direct method of extracting complex refractive index from routine Fourier transform infrared reflectance/transmittance measurements

Braden Czapla, Leonard Hanssen

Author Affiliations +

Proceedings Volume 11485, Reflection, Scattering, and Diffraction from Surfaces VII; 114850D (2020) https://doi.org/10.1117/12.2568502
Event: SPIE Optical Engineering + Applications, 2020, Online Only

Abstract

We describe an algorithm to extract the complex refractive index of a material from reflectance and transmittance measurements commonly taken by spectrophotometers. The algorithm combines Kramers-Kronig analysis with an inversion of Fresnel's equations to provide a direct method of solving for the refractive index which is accurate, even for weakly absorbing materials. We discuss the details of the uncertainty analysis of the algorithm. The algorithm is validated by extracting the complex refractive index of polydimethylsiloxane between 2 μm and 18 μm and comparing against existing literature.

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Braden Czapla and Leonard Hanssen "Direct method of extracting complex refractive index from routine Fourier transform infrared reflectance/transmittance measurements", Proc. SPIE 11485, Reflection, Scattering, and Diffraction from Surfaces VII, 114850D (20 August 2020); https://doi.org/10.1117/12.2568502

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