I Homemade double slit experiment

[desertshaman]

TL;DR Summary

A visible light laser illuminates 2 slits; interference is observed. A photon counter is placed at a dark node. Are photons detected?

Hi :)
So far, this is a thought experiment, which I want to try in the Real.

I want to use a HeNe visible light laser to illuminate a tiny hole in a screen. I will detect photons coming through the hole using a scintillometer, and I expect that an observation screen at the same distance as the scintillometer will show a diffuse distribution of light.
Now I open a 2nd hole in the screen near the first hole, and let it also be illuminated by the laser.
The observation screen now displays an interference pattern of bright and dark nodes.
The scintillometer is moved so that its aperture is placed at a dark node. Are photons detected by the scintillometer?

 

[berkeman]

TL;DR Summary: A visible light laser illuminates 2 slits; interference is observed. A photon counter is placed at a dark node. Are photons detected?

I will detect photons coming through the hole using a scintillometer,

Are you sure that is the instrument you want to use for detecting single photons in your experiment?

https://en.wikipedia.org/wiki/Scintillometer

 

[desertshaman]

Are you sure that is the instrument you want to use for detecting single photons in your experiment?

View attachment 359515

Hmmm. No. I mean a photomultiplier. I beg pardon - last time I saw a scintillometer it was joined to a photomultiplier and I guess I got confused.

I mean something like a Hamamatsu Photomultiplier and counter, for example.
Sorry, Chief.

 

[hutchphd]

Your other choice that might be more useful (albeit more expensive) is a good camera with cooled photosensor. The photomultiplier (even if it is an avalanche photodiode) will not be cheap.
Of course before you buy the sensor you need to ask the question "what is zero in this context?". There will always be some noise, and the signal to noise is what you pay for. How much is enough? What exactly do you wish to know and show?
I have had great satisfaction using cameras that register a few quanta per pixel. These are used for astronomy, fluorescence microscopy and low light spectroscopy. The low light spectroscopy is really multiple slit diffraction and I can attest that it works just as expected.

 

[DaveE]

Be mindful of mechanical noise messing up your interference experiments. You will need a very stable platform to mount everything on. 300nm of relative movement may make the difference between a light or dark spot. Still, people do this stuff often. You can too.

You can just use a camera or a single photodiode initially. Don't try single photon until you've successfully done it with higher intensity. Noise will be a huge issue at low intensity. You'll need really good detectors for that.

 

[desertshaman]

:)
Thank you all for your attention and replies.

Hutchphd - I mostly wanted to use the instrument that I specified because I can find one at a good price.
...
This little project could, I imagine, be carried out for $50, on a good day, using Blu-tak, razor blades, and a distressingly cheap laser pointer (of which there are already too many in the world).
However, it's a side project. My real project is secret, but involves ThorLabs PZT actuators, which I want to observe in motion. This requires good gear such as a stable laser at the very least. So I'll have an opportunity to demonstrate the Great Anomaly.

I'm not incredulous of the reports others have made of double slits, and I don't need to see the experiment repeated for myself.
However, if I could think of a use for covering and uncovering a 2nd slit my attitude would be very different :)

 

[hutchphd]

Good enough. I am a firm believer in the power of blue-tak (the gum of science!) in the optics lab. I have received some askance looks for its use ! I wish you well. Please be forthcoming with any problems...lots of good folks here.

 

[Drakkith]

So I'll have an opportunity to demonstrate the Great Anomaly.

What is the Great Anomaly?

 

[desertshaman]

I have unintentionally been confusing.
I do beg everyone's pardon... I had not thought to be controversial in imagining that (for the layman) "The Great Anomaly" would mean the wave/particle confusion which is an outcome of observing the double slit experiment.
Mark

 

[PeroK]

I have unintentionally been confusing.
I do beg everyone's pardon... I had not thought to be controversial in imagining that (for the layman) "The Great Anomaly" would mean the wave/particle confusion which is an outcome of observing the double slit experiment.
Mark

I have two undergraduate books on QM. The first, by Griffiths, mentions wave-particle duality once, as a historical footnote. The second, Modern QM by JJ Sakurai, doesn't mention it at all.

Wave-particle duality was the unexpected (you could say anomalous) experimental results that QM explained a hundred years ago. There is no wave-particle duality in QM itself.

That said, the writers of popular science books are obsessed with wave-particle duality. Reading or watching most popular science gives you a false impression of QM as a scientific theory.

 

[desertshaman]

Thank you PerotK
I have observed the phenomenon of wave/particle wooh! wooh! very often - sometimes among people who, I see, probably should have known better.
I am glad to have been reassured that others are over that stage.
It's obvious that the study of QM must be taken seriously for several years. I do not see myself putting that work in.
I only want to do some engineering on the micron scale, really, and the double slit experiment came up in my mind when I saw that I might wind up buying a HeNe laser.
Thanks for all your interest! :)
Mark

 

[RicoGerogi]

If you put the photon counter at a dark node, it's not likely to pick up any photons because of the destructive interference. But there could be a tiny chance it detects something due to noise or imperfections in the setup. The experiment might still show some weird stuff in those dark areas, though.