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Laser interference


I was wondering about the possibility of creating full deconstructive interference between two laser beams. I've done rather deep research as best as possible and cannot find a full answer. Basically, I'm wondering if it is possible to cross two lasers and make the beams 'end' where they cross. I know that both lasers would require the exact same frequency and wavelength, and figured a beam splitter and some sort of special mirrors could do that. Theoretically, the two lasers need to be at a 180o phase difference to fully deconstruct. I also read that it is impossible for two lasers to interfere due to their particle like properties and the fact that they contain photons - and photons cannot interfere with each other.


You are quite right about the particle nature of light and about the need for the beams to be exactly out of phase (180o phase difference between them). However "ordinary" interference occurs between two light beams and they are particles also so this is not the problem.

In theory I suppose you could get the beams to interfere constructively but the problem comes when we look at the phase within the photons. They are small packets of energy and one photon from one laser will have a different phase pattern within it from that of the photon from the other laser which it meets. In "ordinary" interference the patterns a double slit arrangement is used. Your beam splitter would make the photons pass one way or the other. The abrupt phase changes between one photon and the next would not prevent interference but would make a "static" interference pattern impossible to see.

However it is not possible for the beams simply to end as you suggest. This would violate the law of conservation of energy.

© Keith Gibbs 2010