  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 advantage and disadvantages of the approach.
