Complex refractive indices measurements of polymers in visible and near-infrared bands

Abstract

The complex refractive indices of polymers have important applications in the analysis of their components and the study of radiation endothermic mechanisms. Since these materials have high transmittance in the visible to near-infrared ranges, it is difficult to accurately measure their complex refractive indices. At present, the data for complex refractive indices of polymers are seriously lacking, which greatly limits the applications of these materials in the field of thermal radiation. In this work, spectroscopic ellipsometry (SE) combined with the ray tracing method (RTM) is used to measure the complex refractive indices of five polymers, polydimethylsiloxane, poly(methyl methacrylate) (PMMA), polycarbonate, polystyrene, and polyethylene terephthalate, in the spectral range of 0.4–2 µm. The double optical pathlength transmission method (DOPTM) is used to measure the complex refractive indices of three polymers, PMMA, polyvinyl chloride, and polyetherimide, in the 0.4–2 µm range. The complex refractive index of PMMA measured by the DOPTM almost coincides with the data measured by SE combined with the RTM. The results show that the trends of the complex refractive indices spectra for the seven polymers in the 0.4–2 µm range are similar. This work makes up for the lack of complex refractive indices in the 0.4–2 µm range for these seven materials and points out the direction for accurate measurements of the complex refractive indices of polymers with weak absorption.

Electrochemically controlled metasurfaces with high-contrast switching at visible frequencies

“…The total height of the PMMA-covered rows is h 1 , and the refractive index of PMMA is n 1 + ik 1 . In the visible wavelength regime, n 1 = 1.5 and k 1 ≈ 0 (45). The other set consists of active pixels, which are gold nanorods locally conjugated with PANI (light blue) in the even rows.…”

Spectral attenuation coefficients from measurements of light transmission in bare ice on the Greenland Ice Sheet

“…2), with and without scattering and absorption interference by the PVC detector rod. The detector rod albedo ω rod ≈ 0.4 is calculated from the absorption spectra of polyvinyl chloride (Zhang et al, 2020); scattering by the rod is assumed isotropic. The Monte Carlo model is integrated over 10 000 interactions at nine wavelengths in 50 nm increments from 350 to 750 nm, allowing us to fit the wavelength dependence of the estimated systematic uncertainty in simulated k att values.…”

Super‐Enhancement Focusing of Teflon Spheres

“…[19,20] In the aspect of the experiment, Peppernick et al used to successfully observe a strong focus near the shadow surface of a polystyrene (PS) sphere (3 m diameter) on a platinum/palladium (Pt/Pd) substrate angularly illuminated by the 400 and 800 nm lasers with a photoemission electron microscopy (PEEM). [21] However, the refractive index of PS sphere at the wavelength of 400 and 800 nm (n = 1.63 and 1.58 [22] ) is much higher than that for Teflon in THz band (n = 1.43 [23] ); moreover, the additional factors, such as Pt/Pd substrate to enhance the collection of emitted electrons for PEEM and angular incidence of laser, complicated the formation of photonic jet and were significantly different from the conditions of the classic Lorenz-Mie theory as well. Zhao et al completed the first experimental observation of photonic jet by a Teflon cylinder at microwave frequencies using a 2D spatial field mapping system.…”