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When excitons exit an electrical circuit and recombine, they create a flash of light which could be harnessed for optical communications.  (Source: Leonid Butov, University of California at San Diego)
Quasiparticle based circuits could break down the electro-optical communication barrier.

One of the bottlenecks in current electro-optical communication systems is the need to convert electrons into photons. While optical interconnects maybe be amazingly fast and efficient, the conversion process still chews up precious time.

This May, Harvard researchers showed a new technology that could be used to build LEDs directly into an integrated circuit. Last week, University of California at San Diego scientists published work in the journal Science using a more direct approach at converting electricity to light on the fly.

Excitons are an interesting type of particle. They are created when photons enter a semiconductor, exciting the electrons it contains. An excited electron forms an electron-hole pair, which in this case, is called an exciton. What makes excitons useful for optical ICs is that when the electron-hole pair recombines, they emit a flash of light.

The key to creating an electro-optical IC in this case is the ability to control the exciton, preventing it from recombining too early. To accomplish this, the UCSD scientists used a special semiconductor made of gallium arsenide, very low temperatures (less than 40 degrees Kelvin), and a special type of exciton that separates the electron and hole pair by several nanometers, confining them to their own quantum wells.

Using voltage to control the excitons, they can be held in place or allowed to flow. Once they flow to the end of the circuit, the electrons and holes recombine, creating photons that can be captured by optical circuitry for use in interconnects or other communication devices.

The group, led by Leonid Butov, a professor of physics at UCSD, has already created several types of exciton-based transistor switches. The switches are quite fast and are able to be manipulated at about 200 picoseconds so far. The exciton circuits are no faster than standard electrical circuits, but removing the clumsy electro-optical conversion allows a much greater data transmission rate between optically connected devices, thus speeding up the process on the whole.

The circuits, operating at 40 degree Kelvin, are far from ready to be used in mainstream applications. Further work will be necessary with other types of semiconductor materials to bring the operational conditions of the exciton circuits to a usable level.

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Nice :)
By Clauzii on 6/23/2008 3:53:28 PM , Rating: 4
They made a Light Show for ants :)

RE: Nice :)
By thornburg on 6/24/08, Rating: 0
RE: Nice :)
By Clauzii on 6/24/2008 9:52:53 AM , Rating: 1
It's like smiling: We use few muscles to smile, a lot more to be angry/sad/negative etc.

I used one line to make someone smile, while You had to use five or six to say how 'stupid' it was.

Get my point?

RE: Nice :)
By thornburg on 6/25/2008 8:41:44 AM , Rating: 2
I used one line to make someone smile, while You had to use five or six to say how 'stupid' it was.

Actually, I used two lines to say it was weird, not stupid, and I got downrated anyway.

I just didn't think it was funny. I could have downrated, but I chose to post a comment instead.

RE: Nice :)
By Clauzii on 6/28/2008 10:26:55 PM , Rating: 2
Hey, I'm cool with that :)

RE: Nice :)
By Adonlude on 6/24/2008 1:51:02 PM , Rating: 3
They made a Light Show for ants :)

The light show will have to be at least... 3 times bigger than this!!!

By murphyslabrat on 6/23/2008 2:55:20 PM , Rating: 2
The circuits, operating at 40 degree Kelvin, are far from ready to be used in mainstream applications.

I've always wanted a reason to use a refrigeration cooler.

RE: Actually...
By amanojaku on 6/23/2008 3:03:12 PM , Rating: 3
Overclocking not good enough? ;-)

By HVAC on 6/23/2008 4:22:12 PM , Rating: 5
200 picoseconds gets you about 6GHz switching speed, I think.

Anyway, as stated before, this is NOT intended as an efficiency exercise. Nobody cares how much power is needed to get the device down to 40 Kelvin. The idea is that we would not need very many of these devices to get blazingly fast internet backbone optical connections. Think national and world level connection speeds, not speed within an optical desktop processor chip.

By geddarkstorm on 6/24/2008 1:35:08 PM , Rating: 2
It's awesome someone finally started using such a simple idea.

It's all well and good for trying to dumb things down, but "excitons" are not a particle, or a quasi-particle--nor is an "electron hole" an actual thing (just as darkness is not actual things, but the absence of light). All this "exciton" thing is, is an excited electron pushed to a higher atomic orbital by the absorption of a photon. When the electron falls back down into its standard, original energy shell, a photon is emitted (but at a lower wavelength than what was absorbed due to energy loss to other quantum processes like heat, transmittance, and quenching) in a process called fluorescence. This is the most basic of physics, so why all this crazy extra terminology that makes it sound like we're dealing with something otherworldly? Excite an electron with a photon, it falls back down and emits a photon--simple! Heck, this process is used to generate X-rays in most X-ray machines, except the excitation comes from high voltage.

Anyways, I bet the reason this is at 40 kelvin, is to address how to keep an excited electron in its excited state, and then actually flow it through the semi-conductor along with the rest of the normal electrons till where you want it to fluoresce. A process that must be done if this is to be used in a circuit. No easy task, but lower temperatures can help "freeze" the excited electron in place it seems. Also, the semi-conductor may have different fluorescent properties at different temperatures, or be unable to do it coherently at all at something above 40K.

40 degree Kelvin?
By kattanna on 6/23/08, Rating: -1
RE: 40 degree Kelvin?
By Chudilo on 6/23/2008 3:20:48 PM , Rating: 1
In full vacuum

RE: 40 degree Kelvin?
By Carter642 on 6/23/2008 3:30:33 PM , Rating: 5
Huh? Where did they say anything about saving energy?

You do realize that the materials used in this experiment are used because they're proven and easy to work with in the lab and arn't destined for production. There are these things called proof of concept demonstrations that are kind of popular.

This isn't going to go replacing your Gb ethernet, it's going to find a home on the backbone routers. Even if they need to have the conversion occur at 100K it would still be feasable to cool the very small volume required by these transistor scale parts. Given the advantages in data rate it would certainly be worth the cooling costs.

Seriously, who said anything at all about this being "green" technology!? Science has been after a direct electro-optical conversion for the last 40 years, this is huge like the memristor, quit being an uninformed reactionary.

RE: 40 degree Kelvin?
By Clauzii on 6/23/2008 3:51:14 PM , Rating: 2
Yes, Huge!

Probably when they get it up to normal temeratures and then into normal chips, the optical CPU's etc. will be very close to reality.

RE: 40 degree Kelvin?
By BladeVenom on 6/23/2008 4:11:29 PM , Rating: 2
They've yet to get superconductors working at any where near room temperaturem and that's relatively old technology.

RE: 40 degree Kelvin?
By zsdersw on 6/23/2008 6:00:30 PM , Rating: 4
Since when do past and present failures speak authoritatively about future potential successes?

RE: 40 degree Kelvin?
By Clauzii on 6/24/2008 1:21:03 AM , Rating: 3
They need to get superconductivity at higher temperatures, yes, but not nescesarily at room temperature. There are relatively cheap means of achieving -40 deg. like peltier. Also here, newer technoligies are possible. One step at a time.

Guess it leaves time to think :)

RE: 40 degree Kelvin?
By achintya on 6/24/2008 3:47:43 AM , Rating: 3
Erm, its 40K not -40 degree (either F or C). -40K does not exist as far as we know(according to the laws of thermodynamics). And achieving 40K (-387.67 degree F or -233.15 degrees C) is not an easy task.

RE: 40 degree Kelvin?
By Clauzii on 6/24/2008 9:59:23 AM , Rating: 2
Oh, -40 deg. Celsius/Fahrenheit, not Kelvin. I know that Kelvin stops at 0. I'll remebmber it next time :)

RE: 40 degree Kelvin?
By Clauzii on 6/24/2008 10:04:21 AM , Rating: 2
Which is 233 Kelvin, btw. I use the term Celsius/Fahrenheit because that's what a Peltier element is rated at.

RE: 40 degree Kelvin?
By kattanna on 6/23/2008 4:04:35 PM , Rating: 1
the energy it takes to bring anything to 40 kelvin is massive. 70F degrees = 294 kelvin and absolute space they say is about 3 kelvin.

so they are expending massively more energy then what would be gained from such efficiency of said circuit.

and while neat as a tech demonstration, i highly doubt it will ever make it out of the labs as anything more then a neat demonstration. unless we suddenly start generating 100 times as much energy for the current price that we do today.

its just an economically unfeasible method to solve said problem.

RE: 40 degree Kelvin?
By masher2 on 6/23/2008 4:17:44 PM , Rating: 5
> "so they are expending massively more energy then what would be gained from such efficiency of said circuit."

This has to do with increasing speed, not efficiency. And as already stated, this is a research project, not an engineering sample. Before this makes it out of the lab, it'll be using real-world materials, at real-world temperatures.

RE: 40 degree Kelvin?
By zsdersw on 6/23/2008 6:15:12 PM , Rating: 2
You "highly doubt it will ever make it out of the labs"? And what sort of authority on the matter are you?

Let me spell it out for you: past and present limitations say nothing about what can and cannot happen in the future.

RE: 40 degree Kelvin?
By sxr7171 on 6/23/2008 8:38:48 PM , Rating: 1
Let's just say the shit they use on backbone networks isn't what they use in your laptop. I hope that came through.

RE: 40 degree Kelvin?
By bighairycamel on 6/23/2008 3:59:50 PM , Rating: 2
Regardless, this is still a very big breakthrough. Imagine harnessing this for an optical communication system.

Given that they could switch at 200pS...
200 pS = 2e-10 sec
2e-10 sec/1 = 5GHz

That gives a theoretical one-way optical transmission of 5,000Mbps.

Now let's say that in real world (non-vacuum/room temp) appications you only see a fraction of that speed and you only achieve 50-100Mbps single way, that still shatters your 20Mbps FioS service.

RE: 40 degree Kelvin?
By repatch on 6/23/2008 4:28:21 PM , Rating: 5

Pretty much ALL discoveries start off like this: Scientists/researchers stumble on something interesting. While not practical in it's current form, they (and others) work on other ways to achieve the same (or sometimes better) results.

Case in point: ever heard of a semiconductor? Ever wonder what the first example of a semiconductor junction (the basis of pretty my all our electronics today) was? Basically it was a very thin wire put just in contact with a crystal of semiconductor material. You had to position the wire in JUST the right spot to work at all, and even then it didn't work very well. You couldn't touch it, heck a sneeze would cause it to stop working:

Look where that discovery has brought us to!

I'm not saying this discovery will be anywhere near as big, but to criticize it based on it's first real example is foolish, and pointless.

RE: 40 degree Kelvin?
By porkpie on 6/23/2008 5:05:44 PM , Rating: 2
40 degree Kelvin??


far more energy is used to get that cold
Way to miss the point.

Next you'll be calling laptops a bad idea because the vacuum tubes inside run down the lead-acid batteries too fast.

RE: 40 degree Kelvin?
By DallasTexas on 6/23/08, Rating: 0
Invention proving to be the mother of neccessity
By DallasTexas on 6/23/08, Rating: -1
By sxr7171 on 6/23/2008 8:40:56 PM , Rating: 2
Are you sure you are posting for the right article? Where did you see anything related to oil or energy consumption in this article?

By BruceLeet on 6/23/2008 8:42:11 PM , Rating: 3
Hihihi Al Gore

By weskurtz0081 on 6/24/2008 1:07:21 AM , Rating: 2
Yeah, because Obama or McCain will magically create an alternative source of energy.... wake up man.

By Entropy42 on 6/24/2008 11:18:08 AM , Rating: 3
Only if we invent things that run on Hope or Ben-gay.

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