In this work we present a simple experiment that may be used to help in the learning of interference and diffraction of light. After an analysis of the Fresnel diffraction theory, the concepts are applied in the understanding of the working principle of the Fresnel zone plates. We present a detailed description of the process used in the production and characterization of the devices, allowing making diffractive lenses with the required focal length for a specific wavelength of operation. The zonal plates produced in this work behave like positive lenses with focal lengths in the range from 8 to 50 cm for light with wavelengths from 630 to 680 nm of a laser pointer.
Fresnel zone plates; Fresnel diffraction
