Determining the continuous thermo-optic coefficients of chalcogenide glass thin films in the MIR region using FTIR transmission spectra

Yuanrong Fang; David Furniss; Dinuka Jayasuriya; Harriet Parnell; Zhuoqi Tang; Angela B Seddon; Trevor M Benson

doi:10.1364/OE.27.022275

Determining the continuous thermo-optic coefficients of chalcogenide glass thin films in the MIR region using FTIR transmission spectra

Opt Express. 2019 Aug 5;27(16):22275-22288. doi: 10.1364/OE.27.022275.

Authors

Yuanrong Fang, David Furniss, Dinuka Jayasuriya, Harriet Parnell, Zhuoqi Tang, Angela B Seddon, Trevor M Benson

PMID: 31510524
DOI: 10.1364/OE.27.022275

Abstract

A new method (FTIR continuous dn / dT method, n is refractive index and T temperature) for measuring the continuous thermo-optic coefficients of thin transparent films in the mid-infrared (MIR) spectral region is introduced. The technique is based on Fourier transform infrared (FTIR) transmission spectra measured at different temperatures. It is shown that this method can successfully determine the thermo-optic coefficient of chalcogenide glass thin films (of batch compositions Ge₂₀Sb₁₀Se₇₀ at. % (atomic %) and Ge₁₆As₂₄Se_15.5Te_44.5 at. %) over the wavelength range from 2 to 25 µm. The measurement precision error is less than ± 11.5 ppm / °C over the wavelength range from 6 to 20 µm. The precision is much better than that provided by the prism minimum deviation method or an improved Swanepoel method.