Throughout my time at LIGO, my work has intimately relied on understanding and characterizing the properties of thin films. This includes minimizing Brownian noise in quarter-wave stacks on small optics and designing and building equipment to map the reflection, transmission, and absorption profiles of the large Advanced LIGO optics. I have also gained experience in designing and simulating the reflection and transmission spectra of different polarizations in thin film designs using Fresnel matrix equations.