How may photons does a LED emit at very low currents?
What is the lowest current where a LED will actually emit photons? Dave does some measurements to answer this quantum physics level stuff!
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What is the lowest current where a LED will actually emit photons? Dave does some measurements to answer this quantum physics level stuff!
Forum: http://www.eevblog.com/forum/blog/eevblog-869-counting-led-photons!/'>http://www.eevblog.com/forum/blog/eevblog-869-counting-led-photons!/
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The 2nd EEVblog Channel: http://www.youtube.com/EEVblog2
Support the EEVblog through Patreon!
http://www.patreon.com/eevblog
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Done.
Interesting to see the non linearity at a very low threshold level. I would anticipate it has something to do with an exponential in the energy of band gap algorithm.
@900 nano Amps how many photons per second are we seeing with human eye ?
The diagram is almost certainly incorrect. The LED does not reach saturation at 500nA …
I would like to train an animal with good night vision to press a button/lever when the LED is on to see how low they can go. In theory they should get close to the photon counter (many animals like horses, deer, lions, cats etc, have a night vision thousands of times more sensitive than a human).
Find the slope and you’ll find Planks Constant
They clearly say the thing has a deadtime. No need to invoke quantum mechanics, dark matter, superstrings, multiverses, Alcubierre drive or false vacuum metastability to explain a basic common sense every day phenomenon of the upper part of the curve bending. The difference between a top optoelectronics scientist and an amateur is that the top scientist actually turns on the basic common sense thinking skills he learned in the kindergarten.
fun fact: an atom in a high brightness LED emits a photon every 15 minutes.
Is that really a Special Edition scope of some kind that Keysight made for you or is it just a standard MSO-X 3054T with a sticker on it?
Dave did you temperature compensate, the output of an led change a lot, depending on the temperature,
Cool experiment
Maybe 250 count is the 'maximum' one would expect, but for their experimentation, they needed only ones with a 200 or lower dark count.
What do you think of using your low voltage sources to apply a very small differential between two opamp inputs and to check if the output is like the open loop gain describes it in the datasheet?
That time Dave tried to shake the electrons out of the cable).
Top YouTubing, Top engineering.
Shouldn't you wrap it in lead bricks to block any background gamma radiation? I think the dark count would drop close to zero.
So 100ms sampling time doesn't have the "vibe" but 1 second does? You could also use 10 seconds, sure the longer the sampling time is, the closer your counts will be to the average. But the average will still be the same. Also, are you sure the Rigol's frequency counter measures the distance between pulses? In that case one would expect it to be all over the place, but it wasn't it actually displayed pretty much the same values as your final setup with he Keysight did (just no average of course) and it also seems to refresh once a second which may suggest it simply counts the pulses (or rising/falling edges) every second and displays whatever it counted…
Superb! I'd love to see the curve all the way up to 20mA.
Oh yeah! I saw that photon counter in your mailbag before but I didn't notice it came from Quebec. I live there!
Great video! Only problem is most people can't afford to buy one of these modules, so it would be really great if you could show us how to build a quenching circuit with a SPAD diode from scratch. There are some "safe" low voltage SPAD's that might work (<40V/thin membrane). If one could scale these into more affordable and safe devices, there are lots of very interesting projects in microscopy, astronomy, medical imaging, quantum physics, and other fields that could open up for the amateur and professional alike. Hanbury, Brown and Twiss were able to determine what was thought to be impossible (a stars diameter beyond the Raleigh limit) using an effective super-resolution technique by photon counting half-a-century ago using only a couple of photon counters. Imagine if you could get an array of these to make a quantum telescope or something no ones has thought of yet.
Awesome, let me do some science with thi- never mind too expensive for a one off…
as already commented by others, the roll-off at higher currents ist certainly caused by the dead-time of the detector and the scope!
You could use an optical attenuator to see what happens at higher currents. You could use some sunglass and measure the transmittance and include the factor in your data readings.
Maybe the reason the diode started up is a combination of factors:
a) it had a few seconds to warm up
b) your shielding of AL foil and electrical tape is not going to stop AM/FM so I'd hypothesize that some of that got through and got detected and rectified just like it does in a Germanium Diode used in an AM radio set.
"Stupid Dual Bloody Button Pain In the Arse Interface, who invented that crap!!?" Couldn't agree more… What a shitty system! Nice investigation though, never thought any photons would radiate at those low currents, very interesting!
I have designed a board for a photon counter, the other guy did the firmware for it and it was a pig to calibrate! Trying to get a batch of them to give below a rated dark count and all perform the same was like trying to catch a fart in a breeze! no wonder they were expensive! It was a very interesting project to do though: quantum physics, electronics – what's not to like! Interesting video! I often wondered this!
Is your powersupply really linear? How does it work? Especially the upper end seems pretty suspicious to me.. You seem to be far away from the saturation of the detector..
Otherwise this might be eplainable by differents layerheights in the diode, some may conduct earlier others later, the laters may be eclipsed, so no light is emitted which hits the detector..
42!!!!! photons 😉
I'd be very interested to know what the graph looks like after 500nA.. Thats where the interesting data would be :/