Transmission Measurements Of Polymer Thin Films

Transmission measurements can be used to study the composition, color, and even the impurities in a material. When that material is formed into a thin sheet of uniform thickness, transmission measurements also can be used to study the material's index of refraction or thickness. The key is an optical phenomenon called thin film interference – the same effect that causes soap bubbles to shimmer with a rainbow of colors when illuminated. In this experiment, thin polymer sheets were analyzed using a NIRQuest512 to determine their thicknesses.

Thin film interference occurs when light reflects from two parallel surfaces and those light rays interfere constructively and destructively. The resulting transmission spectrum then has a sinusoidal pattern of interference called "fringes" superimposed on it.