FireMyLaser said:
Yes it works somewhat decent for a few meters, then it becomes more like a flashlight if you try to match the divergence on both wavelengths.
The reason why it doesn't work is that different wavelengths diffract differently, like white light through a prism. It's the same deal if you use a lens.
One small thing, trivial to some but very important to others. The light
refracts differently, not diffract. Diffraction happens when a wave encounters objects that are spaced on the same order of magnitude as the wavelength of the wave. Refraction happens when moving from one medium to another. A visible light wave doesn't "see" atoms, it "sees" slits like in diffraction gratings, what's when it diffracts. They behave very differently. With optical materials, or really pretty much all solid matter in the case of x-rays, visible light refracts and x-rays diffract.
Another bit of nomenclature for the OP, it's really not a diode in a diode. The cylinder you see is really just a container for the diode, which is actually just the little chip inside the container. With the PS3 diodes, there are 3 diodes, 3 little chips, inside that same cylindrical container, but it is still easy to just say "diode" for the whole thing.
But yes, index of refraction is wavelength dependent. The index of refraction of a prism just has a larger dependence than other materials. You know that expensive "crystal" glassware that people buy? It's really just glass with more lead added to it. The lead increases the index of refraction, but that increase also increases the dependence of the index of refraction on wavelength (if you plot index on y axis vs. wavelength on x axis, it's roughly a negative slope line, top left to bottom right. Putting the lead in moves that line up and makes it steeper, the left side increases more than the right does). So yeah, adding lead to glass makes it cost much more money in the store. And the name "crystal" for that stuff is the worst name ever, since it's still a glass.
