# Wave Demos for ECE 3065 and ECE 4500

NOTE: Different colors are used in the wave animations on this page to distinguish different terms from one another (forward vs. backwards propagating waves, for example). This is not intended to suggest that the light waves are physically at different frequencies (colors) – unless explicitly stated otherwise, all animations on this page are for single-frequency (monochromatic) light, so all of the waves share the same frequency.

Uncompressed movies:

Wave normally incident from air onto n = 1.1 material; reflection coefficient = -0.05 (10 MB)

Wave normally incident from air onto n = 1.5 material; reflection coefficient = -0.2 (10 MB)

Wave normally incident from air onto n = 2 material; reflection coefficient = -0.33 (10 MB)

Wave normally incident from air onto n = 3 material; reflection coefficient = -0.5 (10 MB)

Wave normally incident from air onto n = 9 material; reflection coefficient = -0.8 (10 MB)

Wave normally incident from air onto perfect electric conductor; reflection coefficient = -1 (10 MB)

Compressed movies (may work better if you right-click and download first):

Wave normally incident from air onto n = 1.1 material; reflection coefficient = -0.05 (2 MB)

Wave normally incident from air onto n = 1.5 material; reflection coefficient = -0.2 (2 MB)

Wave normally incident from air onto n = 2 material; reflection coefficient = -0.33 (2 MB)

Wave normally incident from air onto n = 3 material; reflection coefficient = -0.5 (2 MB)

Wave normally incident from air onto n = 9 material; reflection coefficient = -0.8 (2 MB)

Wave normally incident from air onto perfect electric conductor; reflection coefficient = -1 (2 MB)

A distributed Bragg reflector (DBR) is a high-reflectivity dielectric mirror composed of alternating high- and low-refractive index quarter-wavelength-thick layers. Here are some animations to illustrate how a DBR mirror works under normal incidence. In short, the forward-propagating waves (which have been reflected an even number of times) will destructively interfere, while the backward-propagating waves (which have been reflected an odd number of times) will constructively interfere.

Each dashed line in these animations represents an interface. Here is the wave that has undergone zero reflections (15 MB) . This wave is plotted using a blue line in all subsequent animations for reference.

Now we also plot (using red lines) all of the waves that have undergone one reflection (15 MB) . Note that these are ‘in phase’ with each other, and will interfere constructively. So we get a nice big backwards propagating wave when we add them and plot the sum of once-reflected waves (in red) (15 MB) .

By contrast, we note the sum of twice-reflected waves, plotted here in red (15 MB) , is ‘out of phase’ with the never-reflected wave (in blue), indicating destructive interference. If we sum all of these never-, once-, and twice- reflected waves together (neglecting waves reflected 3 times or more), we get the total wave (in red) (15 MB) , with a reduced forward-propagating part and a rapidly oscillating standing wave to the left.

If we add wave 1 (14 MB) and wave 2 (14 MB) , we get a wave propagating in one direction and standing in the other direction (9 MB) . This is common with oblique incidence on a perfect electric conductor, for example.

Animated intensity patterns for the TM1 (14 MB) and TM2 (14 MB) modes in a parallel-plate waveguide.