Measurement of thickness of thin film by fitting to the intensity profile of Fresnel diffraction from a nano phase step

Diffraction of light beams from the phase steps due to the abrupt changes in the boundary of step leads to Fresnel fringes that their visibility and intensity profile depend on the change of the step height or light incident angle. The visibility has been utilized in measurements of different physical quantities. In this paper, for the first time to our knowledge, by introducing the fitting method as a fast method we show that by fitting the theoretical intensity distributions on the experimental intensity profiles of the light diffracted from a step at different incident angles, one can specify the step height with few nano meters precision. In addition, we show that this approach provides accurate film thickness in a broad range of thicknesses using modest instrumentation. Furthermore, based on Fresnel diffraction an optical device is manufactured to measurement of thickness of thin films.