Kirchhoff's Law Broken

retched

Joined Dec 5, 2009
5,207
Turns into a light beam.
The transistor laser has been known for about six years, but its inventors only recently crafted a solution for its miss-match with traditional circuit-theory. In particular, shortly after Georg Ohm defined the first principle of circuit theory—Ohm's Law—Gustav Kirchhoff described the still-universally-taught conservation-of-charge principle, called Kirchhoff's Current Law (circa 1845): "At any junction in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node." But with a transistor laser some of the current goes to creating the laser beam—mixing charge conservation with energy conservation.
But i would like to see some more info.. Patent search anyone? Im sure it will be a while. But it will contain the math.
 
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Markd77

Joined Sep 7, 2009
2,806
I'm no quantum physics expert, but electrons are fundamental particles and can't just be turned into photons. Besides, that would leave the whole apparatus positively charged. If they are just flowing through some kind of nano laser cavity then they come out the other side and no laws are broken.
I suspect this might be the article writer getting carried away.
 

steveb

Joined Jul 3, 2008
2,436
Charge conservation is the most firmly established law in all of physics. This article is completely misrepresenting the physics. Just ignore the claim for now. If there is any truth to it, next week it will be major news, as every established scientific theory will be hogwash.

Think about it. How many electrons can be lost from the circuit before it becomes so positively charged that it rips itself apart? If the electrons are replentished, then you have a circuit somehow, and Kirchoff's law is restored.
 

Wendy

Joined Mar 24, 2008
23,415
I'm no quantum physics expert, but electrons are fundamental particles and can't just be turned into photons. Besides, that would leave the whole apparatus positively charged. If they are just flowing through some kind of nano laser cavity then they come out the other side and no laws are broken.
I suspect this might be the article writer getting carried away.

Yeah, this sounds plausible. According to that logic an LED would do pretty much the same.

Electrons create light by dropping from an excited state to a low energy state, giving off one photon in the process. Coherent radiation is a controlled cascade reaction, where one photon hits an excited electron, causing it to release an identical photon. Where there was one, now there are two, which moves on to create yet more photons. Lasers are amplifiers, and LASER light is created by the amplifier oscillating.

It doesn't have to do this, it is also used for lightwave communications as a straight amplifier too. Took a long time to figure out this trick, but it was an important development.
 

steveb

Joined Jul 3, 2008
2,436
said Feng. "Kirchhoff's Current Law should be redefined as Kirchhoff 's Current and Energy Law."

This is an interesting comment to make. If you discovered a new law of nature in which energy conservation and charge conservation needed to be combined, would you give the credit away by naming the law after someone who lived 150 years ago? Einstein became famous when he combined mass conservation and energy conservation into the law of mass/energy conservation. I don't think he made the suggestion that we call it Newton's law of mass/energy conservation.
 

beenthere

Joined Apr 20, 2004
15,819
The question not asked or answered is how a "transistor laser" is different from a diode laser, especially in the energy-to-photon conversion. A laser diode can do the trick and not misplace any electrons.
 

Wendy

Joined Mar 24, 2008
23,415
Lasers are energy, if it outputs light then some electrons have to move as part of the energy conversion. It occurs to me that it doesn't have to create light and be a laser. The acronym for laser is that of an amplifier (as I mentioned earlier), not an oscillator.
 

beenthere

Joined Apr 20, 2004
15,819
L.A.S.E.R. - Light amplification by stimulated emission of radiation. Gotta be light out, or it becomes a maser. Substitute "microwave" for "light".

From the Physorg article -
Kirchhoff's current law, described by Gustav Kirchhoff in 1845, states charge input at a node is equal to the charge output. In other words, all the electrical energy going in must go out again. On a basic bipolar transistor, with ports for electrical input and output, the law applies straightforwardly. The transistor laser adds a third port for optical output, emitting light.
Here is a link to the operation of a transistor laser - http://spectrum.ieee.org/computing/hardware/the-transistor-laser/3

The IEEE Spectrum article explains part of the function here -
The base current density of 10 000 A/cm2 is 10 or 100 times as dense as that needed for a state-of-the-art high-speed laser, which pulses on and off at perhaps 10 GHz, or with difficulty to over 20 GHz, at a current density of under 1000 A/cm2. Because Feng's HBT is made of direct-gap III–V materials, we speculated that at these normally destructive current densities, light was probably being generated instead of heat. This light would broadcast and remove the energy lost in recombination and not generate excessive heat.
That idea turned out to be on target. In the summer of 2003, we found infrared light that shot out in all directions. Our HBT is both an electrical and an optical signal source driven by the base current. We call it a three-port device: the emitter is grounded with one input being the base, the reverse-biased collector outputs an amplified electrical signal, and the base itself outputs an optical signal when electrons and holes recombine there.
So we are left to imagine that fewer electrons come out than go in to the device.
 

retched

Joined Dec 5, 2009
5,207
A few hundred million of these 'shining' on a PV panel and weve got ove___ity...again.

This is going to light a firestorm for the OUers. And make a bunch of scammers very rich.
 

Wendy

Joined Mar 24, 2008
23,415
L.A.S.E.R. - Light amplification by stimulated emission of radiation. Gotta be light out, or it becomes a maser. Substitute "microwave" for "light".

From the Physorg article -

Here is a link to the operation of a transistor laser - http://spectrum.ieee.org/computing/hardware/the-transistor-laser/3

The IEEE Spectrum article explains part of the function here - So we are left to imagine that fewer electrons come out than go in to the device.
Key phrase highlighted. If it is an amplifier, and there is no light going in, then there will be no light going out. I suspect you're right, but it is a mistake to assume a laser is always a producer of light.

Erbium Doped fibers are true laser amps used in communications, they take a weak optical signal (laser beam) and amplify it 30DB or more. The pumping source is infrared lasers.
 

nsaspook

Joined Aug 27, 2009
13,087
Key phrase highlighted. If it is an amplifier, and there is no light going in, then there will be no light going out. I suspect you're right, but it is a mistake to assume a laser is always a producer of light.

Erbium Doped fibers are true laser amps used in communications, they take a weak optical signal (laser beam) and amplify it 30DB or more. The pumping source is infrared lasers.

Your right, don't get hung-up on visible light.
We use UV lasers at work to shoot the photo masks on wafer resist. http://en.wikipedia.org/wiki/Excimer_laser

http://www.icknowledge.com/misc_technology/Photolithography.pdf

At some point in the energy spectrum mass and energy are the same. So maybe there's a little fusion reactor inside that transistor.:eek:
 

Wendy

Joined Mar 24, 2008
23,415
Actually communications lasers are infra red. Their frequencies are very precision, so they can have many different lasers down the same fiber, each a separate channel. Last I heard they used a 40GB data rate, but that is extremely old news. I suspect they are much faster now.
 

Thread Starter

Clay

Joined Feb 12, 2010
21
Thanks for all of the responses. I am kind of skeptical myself.
Not like the EETimes to spread rumours. Maybe a slow news day
and an up-all-night reporter? If you didn't see it on the 'Net', it never happened,right?

Best regards,

/Clay
 
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beenthere

Joined Apr 20, 2004
15,819
It's kinda odd. Let a power transistor get hot (emit IR frequency photons), and nobody claims diddley. Why is it different when the light frequency is visible? There is no mention of terminal currents.
 
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