Polymethyl methacrylate: Optical properties from 191 to 1688 nm (0.735–6.491 eV) by spectroscopic ellipsometry

Poly(methyl methacrylate) (PMMA), known commercially by the trade name Plexiglas®, is an important polymer with numerous applications. This acrylic-based glass is often used as an alternative to conventional glass. Herein, the authors derive the optical functions of PMMA from reflection spectroscopic ellipsometry (SE) and transmission ultraviolet-visible intensity data. These functions were obtained from a 3 mm thick commercial sample of PMMA from 191 to 1688 nm. Reflection SE data were taken from the polymer surface at three different angles of incidence, where the backside of the sample was roughened prior to these measurements. To model the small absorption of the PMMA, transmission intensity measurements were also obtained with an ellipsometer at normal incidence to the sample surface. Both the reflection and transmission data were reasonably fit using a summation of a Cody-Lorentz oscillator and 14 Gaussian oscillators to account for absorptions in the sample. The optical functions obtained in this work agree well with previously reported values. For example, the authors obtained the following n_x values, where x is the wavelength in nanometers, of n₃₀₀ = 1.528, n₅₀₀ = 1.492, and n₁₀₀₀ = 1.479.