Refractive index and thickness determination of thin-films using Lloyd's interferometer

摘要

Determination of the refractive index and the thickness of thin-films using light interference have been presented. This has been done, for the first time, with the use of Lloyd's interferometer. The mean idea is based on using the sample in two different positions in the same interferometer. The method has been applied for four different samples with different thickness. The thickness is measured using a reflection regime in a separate step. In case of determining both of refractive index and thickness of the thin films, the needed data have been obtained directly from a comparison between two interference fields in the same interferogram for each case. In this way we avoid mistakes that could be produced from the direct experimental measurements. The method with its simplicity, in experimental mounting and mathematical interpretation, can offer quite accurate results. An investigation of the uncertainty in the measured values demonstrates that, for the measured thickness we have a tolerance of 3% and for refractive index the tolerance is ±0.002, which is the reasonable for two-beam interference systems.