I Double-dark Slit Interference Pattern?

[Quarker]

A classical double-slit experiment using a laser as the light source creates an interference pattern. Has anyone ever performed an additional double-slit experiment where only the dark fringes of the interference pattern are projected, specifically to see if an additional interference pattern is created? In theory, the screen should be dark in such a situation. If a double-dark slit experiment creates an interference pattern, it would be hard to explain using current physics.

 

[renormalize]

Has anyone ever performed an additional double-slit experiment where only the dark fringes of the interference pattern are projected, specifically to see if an additional interference pattern is created?

Can you post a diagram of the configuration you're asking about?

 

[PeroK]

You mean like making a black pudding that's so black that even the white bits are black?

 

[Quarker]

Can you post a diagram of the configuration you're asking about?

Not at the moment, but it’s simple enough to describe. Use the interference pattern created by the laser, and block all light modes, so that only dark modes are projected onto a second screen.

 

[Quarker]

You mean like making a black pudding that's so black that even the white bits are black?

Nope, not even close.

 

[PeterDonis]

block all light modes, so that only dark modes are projected onto a second screen.

What do you mean by "light modes" and "dark modes"?

I strongly suspect you are not familiar with the actual math here.

 

[Ibix]

I think he means to project an interference pattern onto a screen, then cut holes in that screen where the minima are and see if you get patterns on a second screen placed after the first.

You can model the screen with holes as a set of very dim sources. You would need to worry a lot about incoherent illumination from the failure of the laser source to be perfectly coherent, which is certainly a significant contribution to the illumination and possibly even the dominant one depending on how wide your slits are. You'd also need to model the phase and intensity variation across the slits.

Modelling it is mathematically messy but not really difficult. Actually doing it is stupidly difficult because you throw away most of your light. I'd doubt anyone has done it because it doesn't tell you anything particularly new. It's just Fourier optics.

 

[Quarker]

What do you mean by "light modes" and "dark modes"?

I strongly suspect you are not familiar with the actual math here.

Possibly. The interference pattern created by the laser consists of alternating light and dark areas projected onto a screen. If two additional slits are created in that screen that lie completely within two dark areas (fringes), so that no light can be projected onto a second screen, the second screen should be dark. But as far as I can tell, no one has ever done this experiment to verify that. And if the dark fringes create a second interference pattern, that would be something entirely unexpected. But since it’s a possibility, it should be tested for. It could be the explanation for this: https://www.physicsforums.com/threa...aser-beam-through-an-aom.1079105/post-7249915

 

[Quarker]

I think he means to project an interference pattern onto a screen, then cut holes in that screen where the minima are and see if you get patterns on a second screen placed after the first.

You can model the screen with holes as a set of very dim sources. You would need to worry a lot about incoherent illumination from the failure of the laser source to be perfectly coherent, which is certainly a significant contribution to the illumination and possibly even the dominant one depending on how wide your slits are. You'd also need to model the phase and intensity variation across the slits.

Modelling it is mathematically messy but not really difficult. Actually doing it is stupidly difficult because you throw away most of your light. I'd doubt anyone has done it because it doesn't tell you anything particularly new. It's just Fourier optics.

If two dark minima create an interference pattern, assuming they are truly dark, that would most certainly tell you something new.

 

[Ibix]

If two dark minima create an interference pattern, assuming they are truly dark, that would most certainly tell you something new.

Sit in a dark room. Now you have two sources of no light with sources of no light between and around them. Do you see interference patterns all round you?

 

[Quarker]

Sit in a dark room. Now you have two sources of no light with sources of no light between and around them. Do you see interference patterns all round you?

So you’ve done the experiment?

 

[Ibix]

So you’ve done the experiment?

What, sitting in a dark room? I did a tech job developing film one summer and spent half of it in a dark room. No interference patterns that I saw.

 

[weirdoguy]

So you’ve done the experiment?

Everyone did at some point in their lives, most of us during the night, when we sleep.

 

[weirdoguy]

I think your problem is that you think that "dark" means that there is something that is dark. But no, it means there is nothing. So you want to do an experiment on nothingness. That's why it's kind of, no offence, silly.

 

[Ibix]

I think your problem is that you think that "dark" means that there is something that is dark. But no, it means there is nothing. So you want to do an experiment on nothingness. That's why it's kind of, no offence, silly.

Also unless the slits are zero width there will be some light illuminating them from the primary pattern. So @Quarker would get some pattern (maybe interference, maybe not, depending on how coherent the source was and the experiment geometry), but all due to light leakage.

If you idealise the experiment you have no light. It doesn't become some light just because the light illuminating the second grid is a double slit pattern. To get something from nothing like that you'd have to invent a new theory of electromagnetism that allowed it to happen while still being compatible with the enormous body of experimental evidence compatible with the current theory, including single-photon experiments that already test super low light levels. I'm sure if you fronted the cash you could find someone who'd do the experiment for you without such a theory (although see my first paragraph), but otherwise why would they waste their time when there are other lines of research with a solid theoretical basis?

 

[PeterDonis]

It could be the explanation for this: https://www.physicsforums.com/threa...aser-beam-through-an-aom.1079105/post-7249915

Your "this" here is just the same unwarranted speculation in another thread. That's not a good idea.

So you’ve done the experiment?

If you really think it's worth an experimenter's time to put a light detector in a completely dark room (no light source anywhere) and take readings of what it outputs, then you're welcome to invest the time and effort to do it yourself. Let us know what you find out.

In the meantime, this thread is closed as the OP question has been well answered. Thanks to all who participated.