Can you use a laser to measure the speed of light with a rotating mirror? I have learned that the classical measurement of the speed of light with a rotating mirror does not work with a laser (as opposed to, say, a mercury-vapor lamp).
Can you tell me if and how coherency of light is necessary/contraindicated for the success of this experiment?
 A: Coherence of light doesn't harm this experiment because this experiment is based on geometric optics. However, laser is actually an immensely good source of light which has a very well-defined direction of the light rays. That's why it's much better to use a laser as the light source than the candles or whatever Foucault used to use.
To see a web page of people who have repeated the Foucault rotating mirror measurement of the speed of light using a He-Ne laser, see e.g.

http://www.pas.rochester.edu/~pavone/particle-www/teachers/demonstrations/FoucaultDemonstration.htm

A: Did the Wikipedia article specifically mention using a rotating mirror with laser light? When I was in undergrad we used a pulsed laser to measure the speed of light, but not with a rotating mirror. We split the beam and directed one one half at a photodiode. The other half was sent across a long room a few times with mirrors before hitting the photodiode. We used the timing measurement from the photodiode and manually measured the path length. 
