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Do 2 laser beams interfere?

by DParlevliet
Tags: beams, interfere, laser
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Nov6-13, 03:37 PM
P: 133
I have a question about this old (closed) Thead about the quote:

"....but also two separate very low intensity laser beams have been sent through single slits to a common detector and a diffraction pattern resulted. The intensity was so low that the probability of a (semi-classical) photon being between the slits and the screen was close to zero." (from Oz)

I suppose two lasers don't each emit a photon at the same time. So if one photon is emitted by one laser (and not by the other laser) with which wave does the photon interfere?
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Nov6-13, 03:57 PM
jtbell's Avatar
P: 11,875
My understanding is that in such an experiment, the two lasers have to be coupled or "locked" to each other in such a way that there is no information about which laser any individual photon comes from. This makes it analgous to a double-slit experiment with a single laser as a source, in which there is no information about which slit any individual photon passes through.
Nov7-13, 05:59 AM
P: 133
Two lasers must be synchronizes to be sure that the photons has the same phase. But can lasers be locked that both also emit a photon at the same time?

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