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I would like a suggestion on a price-efficient way of experimenting with spontaneous down-conversion and single-photon counting. The simple dual-slit experiment could be one part of an application although there are many, but I'm mainly asking about the key components which are similar - the laser that pumps a SPDC-crystal, the crystal itself, and photon-counters (the other standard optical bench items I'm more familiar with).

For example, is a 405 nm (blue) diode-laser module the way to go, with a BBO-crystal, and what to use for detectors - are avalance photo-diodes good enough? What kind of quality does the laser need to have (wavelength stability etc)?

I know there is a Journal of american physics teachers or something which have articles covering these fundamental experimental setups now and then, but I thought I'd ask here in case anyone who works at a lab (with limited funding :) with a good setup could share some ideas.

If this gets many answers, it should be turned into a community wiki entry I guess.

BjornW
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2 Answers2

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The traditional method is with a photomultiplier tube or PMT. These are very expensive but are easily recognized and you might try hanging around the auctions at the local research university to see what comes up.

More modern is the Avalanche photodiode or APD. Amazingly, my favorite electronics supplier, Digikey, has them, at this time as cheap as $942. These might be harder to spot at the auction (as they are quite small).

Never fear, this is another alternative. The maker of the Digikey APDs is Advanced Photonix Inc which offers them only through Digikey, at least according to their website.

If I were an aspiring young scientist, I might consider contacting API and seeing if they were willing to loan me a "solder sample" (out of spec) APD. Before contacting them I would do the following:

(1) Get the data sheet for their most common and cheapest part.

(2) Study the data sheet enough to completely understand the part.

(3) Design a circuit that will use the part in a manner so as not to damage it.

(4) Send the proposed design to an API sales / support engineer using their contact form.

(5) Apply prayer.

(6) If it didn't work, repeat with another APD maker.

The sad fact of engineering is that the sales reps give away free samples to engineers who almost never use them. If you happen to known someone in an industry which uses APDs, they may have some sitting around in their desks that they couldn't care less about. I'd be willing to bet that there are LHC engineeers / physicists who would have a few lying around.

To get one, you might consider using your contacts to find someone connected to you who works at one of the colliders. If you're at a big school, it should be easy to use google to find a prof who's in a collaboration.

Carl Brannen
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Berkeley's undergrad lab should have a competitively cheap setup. Here's the wiki. You might be able to contact the lab manager for more information, which can be found through here.

As predicted in the last answer, it's APDs and BBOs.

emarti
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