I really wished I had seen this a few days ago... Why is this information so rare? "Optics: Two-beam interference - diverging beams | MIT Video Demonstrations in Lasers and Optics" and "Optics: Two-beam interference - collimated beams | MIT Video Demonstrations in Lasers and Optics" demonstrate this a little bit; but lack the explanation (though one of them adds an additional spreader in the mix and emphasizes the circular character... Most everything else I've seen says that the interferometer would have produced vertical fringes - but I suppose that's because of the diagonal that every little bit is a slightly longer path and those waves would interfere destructively(with even a ideal columniation) - at the splitter even, well before the final output... or even in the space after the splitter. I got some various things from amazon - but this cube splitter I can't seem to get any interference... while most things seem to use more of a slide of glass; I wonder if the interface that makes this cube splitter is too thin.
Hi Stephen, Hope you are doing well. Thank you for the nice explanation. I recalled this in my 3rd year physics experiment that we had to do an oral presentation after. This question was definitely asked but I provided the same cliche answer that probably from an old text book. Now after watching the way you approach to this question, I am ashamed. Thank you!!
The short answer is - the detection plane is presented with a spherical wave front but plane wave front. When a spherical surface meet with a plane surface the central location meets the wave front sooner than its periphery that causes a phase shift in the radial direction like a ring of constructive and destructive pattern.
Hi stephen! Is there a way in contacting you? Im doing the same experiment in uni but im having problems getting the info of the laser/bullseye on the arduino camera. How did you get the data?
So basically as I understand it and i think thats what you explained, is that we get the fringes simply due to the fact that light diverges and when the two mirrors are not exactly the same distance this divergence in the two beams of light is no longer at the same angle, the angle then overlaps causing interference to only occur at some parts. Makes sense. The problem i then have is when you keep moving the one mirror further away you get a repeating effect of the fringe pattern showing up and then disappearing over and over again. What would cause the absence of the interference when the beam angle is not equal?
It's been my experience that the interference fringes are always there. They expand outwardly or inwardly as the mirror moves, but they don't go away. Here is a video that demonstrates the response of the bull's-eye to mirror movement: ua-cam.com/video/TZ8RdkXv2Fs/v-deo.html Two spherical waves are interfering. When one mirror moves, the relative phase between the spherical wavefronts changes. When projected onto a planar surface (the screen), the value of this relative phase depends on the radial coordinate. All that can happen when a mirror moves is that the fringes move. The dark spot that comes and goes in the center of the bull's-eye is just a result of the relative phase at that exact location, and it cycles from 0 to 2*pi as the mirror moves. In some experiments, a photodiode is positioned there and the resulting sine-wave output of the photodiode corresponds then to the fringe spacing.
@@stephenremillard1 well in the MIT video series on the subject the fringes show up in a distance of the optic inside the laser they use. Maybe it doesn't work that way when using a diode laser
@@wynand988 I think that the appearance of interference fringes inside the laser optics over a short range of OPL is likely due to additional wave interactions than the two simple interactions that I used in my analysis. Well, must be so. If you have it, can you share the link, with a time stamp. I'd like to take a look at it.
Yes, it is completely within your right to do so. Although this isn't peer reviewed, so your professor might not consider it a suitable reference. I do suggest asking your professor about that. Thanks for asking me, and thanks for the compliment.
your channel is a goldmine. regret I didn't find it earlier. so good content. thanks
Thanks!
Thank you ! This is exactly what I want
Thank you for this. I appreciate this video greatly and also appreciate that you care enough to go into detail on this. Thanks again!
I really wished I had seen this a few days ago... Why is this information so rare?
"Optics: Two-beam interference - diverging beams | MIT Video Demonstrations in Lasers and Optics" and "Optics: Two-beam interference - collimated beams | MIT Video Demonstrations in Lasers and Optics" demonstrate this a little bit; but lack the explanation (though one of them adds an additional spreader in the mix and emphasizes the circular character... Most everything else I've seen says that the interferometer would have produced vertical fringes - but I suppose that's because of the diagonal that every little bit is a slightly longer path and those waves would interfere destructively(with even a ideal columniation) - at the splitter even, well before the final output... or even in the space after the splitter.
I got some various things from amazon - but this cube splitter I can't seem to get any interference... while most things seem to use more of a slide of glass; I wonder if the interface that makes this cube splitter is too thin.
Hi Stephen, Hope you are doing well. Thank you for the nice explanation. I recalled this in my 3rd year physics experiment that we had to do an oral presentation after. This question was definitely asked but I provided the same cliche answer that probably from an old text book. Now after watching the way you approach to this question, I am ashamed. Thank you!!
Wow, you are the king!! Thanks
Very nice explanation. Thank you!
The short answer is - the detection plane is presented with a spherical wave front but plane wave front.
When a spherical surface meet with a plane surface the central location meets the wave front sooner than its periphery that causes a phase shift in the radial direction like a ring of constructive and destructive pattern.
Hi stephen! Is there a way in contacting you? Im doing the same experiment in uni but im having problems getting the info of the laser/bullseye on the arduino camera. How did you get the data?
So basically as I understand it and i think thats what you explained, is that we get the fringes simply due to the fact that light diverges and when the two mirrors are not exactly the same distance this divergence in the two beams of light is no longer at the same angle, the angle then overlaps causing interference to only occur at some parts. Makes sense.
The problem i then have is when you keep moving the one mirror further away you get a repeating effect of the fringe pattern showing up and then disappearing over and over again. What would cause the absence of the interference when the beam angle is not equal?
It's been my experience that the interference fringes are always there. They expand outwardly or inwardly as the mirror moves, but they don't go away. Here is a video that demonstrates the response of the bull's-eye to mirror movement: ua-cam.com/video/TZ8RdkXv2Fs/v-deo.html
Two spherical waves are interfering. When one mirror moves, the relative phase between the spherical wavefronts changes. When projected onto a planar surface (the screen), the value of this relative phase depends on the radial coordinate. All that can happen when a mirror moves is that the fringes move.
The dark spot that comes and goes in the center of the bull's-eye is just a result of the relative phase at that exact location, and it cycles from 0 to 2*pi as the mirror moves. In some experiments, a photodiode is positioned there and the resulting sine-wave output of the photodiode corresponds then to the fringe spacing.
@@stephenremillard1 well in the MIT video series on the subject the fringes show up in a distance of the optic inside the laser they use. Maybe it doesn't work that way when using a diode laser
@@wynand988 I think that the appearance of interference fringes inside the laser optics over a short range of OPL is likely due to additional wave interactions than the two simple interactions that I used in my analysis. Well, must be so. If you have it, can you share the link, with a time stamp. I'd like to take a look at it.
wow this explains a lot!
Is it ok if i referece you in one of my assignments?
Thanks a lot for explaining it so clearly.
Yes, it is completely within your right to do so. Although this isn't peer reviewed, so your professor might not consider it a suitable reference. I do suggest asking your professor about that. Thanks for asking me, and thanks for the compliment.