Can interferometers be built with multiple light sources?

[Xilor]

Hi, it's probably a stupid question, but I was wondering if it's possible to build interferometers with two perfectly calibrated lasers at the same wavelength. Would the same sort of results appear as with a single source of light, or does the fringe shifting effect only appear when the photons come from the same source?

 

[sophiecentaur]

The two lasers need to be phase locked by coupling them together in some way, to avoid drift. This is not too hard to do and what you end up with is effectively one bigger laser.

I know it's tempting to talk about photons (by assuming that they help the explanation) but EM waves are waves too and you may as well describe what goes on in terms of waves. Trying to make a half arsed explanation that revolves around a flawed picture of photons is really not going to work. Photons are a LOT harder than waves! (Ask anyone who knows)

 

[Xilor]

You mention that it would be like one bigger laser, to be sure that I don't misinterpret a small ambiguity: It is possible to place the two lasers in different positions/angles? Would it be possible to measure if two intersecting beams have exactly the same length by using two lasers and a beamsplitter+detector at the intersection?

I mainly used the word photon because I thought that the effect might rely on the superposition of the particles, which I figured could work differently if the arriving waves from the two possible travel directions came from two different sources.