Total internal reflection and evanescent waves
The transition from refraction to total internal reflection is not instantaneous for real waves. Finite beam width implies the presence of both sub- and supercritical incidence angles. Also, waves incident above the critical angle still penetrate several wavelengths into the optically rarer medium in the form of an evanescent wave.
Polarization:
IOR ratio:
Tips for trying:
- Set the angle of incidence a little over critical and observe the shape of the reflected and transmitted parts of the wave.
- As the beam width grows, compared to wavelength, the incident wave gets more similar to a plane wave. See how the imperfections disappear but the evanescent wave broadens. In contrast, narrow beams result in strong distortions.
- The small lateral shift with respect to the marked axis of an ideal reflected beam is caused by the fact that the reflection does not happen strictly on the interface plane. This is known as the Goos–Hänchen effect.
- For p-polarized wave there is Brewster's angle in which the reflection coefficient drops to zero. Can you find it?
- Note for big differences in optical density how the wavelength changes for the transmitted wave. Also, what happens in normal incidence?
- The plot shows the magnetic field, which for μr = 1 is continuous on a dielectric interface. You can zoom in by setting a large wavelength.
- The simulation won't let you choose beams with Rayleigh length smaller than the viewport.