Diffraction of Plane Waves by a Small Aperture

Student thesis: Master thesis (including HD thesis)

  • Niels Maribo Bache
  • Steffen Skjødt Kondrup
4. term (FYS10), Physics, Master (Master Programme)
This report investigates how plane waves are diffracted by a screen with a small aperture.

Classically a screen with infinite extend, infinitesimal width, infinite conductivity and a circular aperture is considered. Using Kirchhoff's approximation, an expression of the diffracted electric field is derived. This field is computed and plotted by approximating the aperture field as a constant field and as a free plane wave.

Quantum mechanically a screen with infinite extend, finite width, finite conductivity and a cylindrical aperture is considered. We expand Babinet's principle to a screen with finite width and conductivity. The single electron wave functions and energy levels are found using the particle in a box approach. The conductivity tensor is found analytically for $0K$ and is used to calculate the current density numerically. The dyadic Green function is derived in cylindrical coordinates and used to calculate the scattered electric field of the cylinder numerically.
Publication date10 Jun 2014
Number of pages65
ID: 198660630