Diffraction of light from a long rectangular phase slit.

Abstract

The phenomenon of light diffraction from an opaque screen containing a long rectangular slit has a closed-form solution in the Fraunhofer regime, which is covered in the undergraduate physics curriculum and experimentally verified. Here, we examine the more general situation of a semi-transparent plane that contains a long rectangular slit. Our analysis reveals that the diffraction patterns differ significantly between two specific cases: diffraction from an opaque screen containing a slit, and diffraction from a transparent plane featuring a slit (phase slit or a phase strip). The calculations demonstrate that the diffraction pattern resulting from the phase slit comprises two distinct sets of fringes with different spatial frequencies, and the width (size) of the phase slit (or strip) can be determined by examining the lower-frequency fringes. To verify these calculations, we fabricated appropriate phase slits and phase strips and analyzed their diffraction patterns. Our experimental findings showed excellent agreement with the theoretical predictions.