I'm looking for a impressive, inexpensive lecture demonstration of optical standing wave resonance. Preferably visible light. Can anyone suggest such a demo?
Before we go too far ... the wavelength of visible light is about half a micron. If you do succeed in setting up standing waves, and figure out how to visualize it, you won't be able to see the wave pattern themselves. The wavelength is too small. You might be able to visualize the increased intensity in the cavity, though. I've seen that in plastic waveguides. It's quite dramatic, and pretty much just what you are looking for. But I don't think a waveguide solution would be quick and inexpensive to set up. One problem with free-space cavities is getting the cavity to be stable. It doesn't take much of a mis-alignment to ruin the resonance. Waveguides take care of that.
You might try a Plexiglas or Lexan rod with polished ends. Or perhaps those multimode fibers that are used in some Christmas trees. A Helium Neon laser. A laser pointer might work. None of these ideas will work the first time. It will take some trial and error.
Maybe someone else has a better idea.