Metamaterial infrared refractometer for determining broadband complex refractive index

Infrared refractive index is an indispensable parameter for various fields including infrared photonics. To date, critical-angle refractometers, V-block refractometers, and spectroscopic ellipsometry have been commonly used to measure the refractive index. Although every method has an accuracy of four decimal places for the refractive index, a measurable wavelength region is limited up to about 2 mu m. In this study, we demonstrated a metamaterial infrared refractometer for determining broadband complex refractive index. Using the device, a broadband (40-120 THz; wavelength 2.5-7.5 mu m) and high-precision(< 5 x 10(-3)) complex refractive index of polymethyl methacrylate was measured for the first time. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement