- #1
johng23
- 294
- 1
Are there any tricks for getting the two arms of a Michelson interferometer exactly equal, if all I have is a CW HeNe laser to align? The real experiment will be using the interferometer on short pulses, so I will only see interference when the path lengths are equal to within 30 microns or so. I can't think of any way, since the coherence length is probably 10's of centimeters.
I saw some website that was saying that as you scan the delay of one arm, the fringes will move in one direction, and when you pass the equal length point, they will move in the opposite direction. But that makes no sense to me. Maybe I'm just not seeing it, but if I visualize scanning two beams past each other, the fringes continually move in one direction, and the absolute difference in phase is not discernable.
I saw some website that was saying that as you scan the delay of one arm, the fringes will move in one direction, and when you pass the equal length point, they will move in the opposite direction. But that makes no sense to me. Maybe I'm just not seeing it, but if I visualize scanning two beams past each other, the fringes continually move in one direction, and the absolute difference in phase is not discernable.