Aperture plates for Fraunhofer diffraction

Abstract

An undergraduate experiment on Fraunhofer diffraction is described. The apertures are made by electron beam lithography in a chromium film on an optical flat, giving a marked improvement of performance over glass photographic plates. Computer control of the electron beam allows complex repetitive apertures to be constructed giving clear demonstrations of the principles of Fraunhofer diffraction. The light source is a 1 mW helium-neon laser. Patterns from simple apertures may be measured to obtain a quantitative test of the theory and more complex apertures illustrate theory such as the use of superposition and the convolution theorem.