Re:military research, again (Score 1)

But my primary thought is: Wouldn't any dust particles get vaporized by the beam? How do the characteristics of this situation vary from lasers to masers?

I get to play with some reasonably high power lasers at work - dust is a problem but one that can be solved.

The power densities that some lasers put out is greater than the power per unit area exiting the surface of the sun. This isn't a problem so long as nothing in the high power density region absorbs the wavelength of light that the laser is running at - as long as the optics are transparent the light goes in, gets bent around, and comes out the other side without causing any heating. If, however, a speck of dust lands on some part of the optics chain with a concentrated beam it can absorb the light and becomes a hot spot that damages optical coatings and scatters light out of the optical path.

The main cure for this is hermetically sealing the optical path, or at least operating it in a very clean environment. At some point the laser has to exit the system to be useful, so tricks like flowing pure nitrogen boiled off from a liquid N2 source over the output lens are used. The pure gas contains essentially no dust and provides a buffer layer to the dirty outside air.

I once ran a system like this in an area that was supposed to be a cleanroom, but the filtering system wasn't working properly. Every once in a while a bit of dust would pass through the beam and cause a bright flash as it scattered light and burnt to a crisp. Good times.