Complex refractive index measurements of poly(methyl methacrylate) (PMMA) over the UV-VIS-NIR region

Abstract

Poly(methyl methacrylate), PMMA, is a popular polymer for optical applications due to its superior transmission and reflection. However, its optical properties in the ultraviolet regime still need to be thoroughly studied. Using the reflection-transmission method, we determine its complex refractive index by numerically analyzing the measured data from thin films. The PMMA standalone film is fabricated by peeling off its substrate after spin-coating. Its transmittance and reflectance are then measured in a spectrophotometer using an integrated sphere. The complex refractive index n + ik is extracted theoretically from the measured transmittance T and reflectance R. The uncertainties of measured n and k are discussed in the two limits of strong absorption and weak absorption of the materials to illustrate the advantages and disadvantages of the approach.