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Nanoscale Terahertz Optical Switch Breaks Miniaturization Barrier

Soulskill posted about 5 months ago | from the who-cleans-up-all-these-broken-barriers-anyway dept.

Science 35

Science_afficionado writes "There is a general consensus that ultimately photons will replace electrons running through wires in most of our microelectronic devices. One of the current technical barriers to the spread of optoelectronics has been the difficulty in miniaturizing the ultrafast optical switches required. Now a team of physicists at Vanderbilt has made terahertz optical switches out of nanoparticles of vanadium dioxide, a material long known for its ability to rapidly change phase between metallic to semiconducting states (abstract). They report in the Mar. 12 issue of Nano Letters that they have created individually addressable switches that are 200 nm in diameter and can switch between transparent and opaque states at terahertz rates."

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Isolation, Reflection and Cross-talk (2, Interesting)

Anonymous Coward | about 5 months ago | (#46486895)

There doesn't seem to be any mention of these. AFAIK these are important characteristics. If the switch has poor isolation, it's not a very good switch. If it reflects too much, it will cause havoc in the system. At the nano scale all of these properties become more and more significant.

Re:Isolation, Reflection and Cross-talk (-1)

Anonymous Coward | about 5 months ago | (#46487003)

Also, 200nm might be a new record, but they fail to put that into context with existing electronic chips that are down in the 14nm range in current production. Considering existing technology will continue to be engineered even smaller while anything new is busy with the long process of making it from the lab to the factory, if your new experimental thing isn't at *least* an order of magnitude better than current production, there's little point pursuing it in commercial directions (although it's still a useful research exercise on the pathway to eventually reaching something pragmatic).

Re:Isolation, Reflection and Cross-talk (1)

TWX (665546) | about 5 months ago | (#46487351)

So you're saying that it won't be able to connect to my legacy 62.5um OM1 FDDI fiber then?

Re:Isolation, Reflection and Cross-talk (0)

Anonymous Coward | about 5 months ago | (#46487357)

Size matters only when space is limited. For applications that aren't limited to the size of a cell phone, this technology can provide and huge leap forward in computation on a larger scale.

Re:Isolation, Reflection and Cross-talk (2)

cas2000 (148703) | about 5 months ago | (#46487583)

most chip production is still at 28nm or larger, so 200nm is less than 10 times larger....which is still a negative.

on the positive side, though, it switches at terahertz rates - and even assuming that means only 1 Thz, that's still 200-250 times faster than the roughly 4-5 Gigahertz that current top-of-the-line CPUs switch at.

10 times the size for 250 times the speed...for non-mobile applications like a desktop or server CPU - or for a GPU - the larger size would almost certainly be worth it.

Re:Isolation, Reflection and Cross-talk (2)

alannon (54117) | about 5 months ago | (#46488729)

The problem is: current CPU designs are frequently limited by wire propagation delays. Optical circuits do have somewhat faster propagation than copper (1c vs 0.75c), but increasing the size of components necessarily increases the distance between them. 1 thz = 1 * 10^-12 light seconds, which is 0.3mm, I believe.

Re:Isolation, Reflection and Cross-talk (1)

HiThere (15173) | about 5 months ago | (#46489231)

Worse, C is the speed of light in a vacuum. In any other medium it's slower. I'd need to check what current light fiber speeds are, but it's guaranteed to be less than C, unless there's a vacuum in the center of the fiber. (I think there needs to be a relatively smooth gradient of speeds, with the center being the fastest and the edges being the slowest for an optical fiber to work, but I'm less than certain.)

OTOH, a tetrahertz switch doesn't mean a tetrahertz CPU cycle. So I'm not at all sure that you can presume that we're talking about a speedup of 250. I don't know what the speed of a switch inside a fast CPU is currently.

Re:Isolation, Reflection and Cross-talk (1)

K. S. Kyosuke (729550) | about 5 months ago | (#46492181)

The copper propagation only applies to wide interconnects. The narrow ones are several times slower. Having said that, you probably wouldn't use the optical link for local interconnects unless you had full optical replacements for traditional gates. Regarding the gradient, I think it's the other way round - you want to achieve total internal reflection to keep the light inside, so you need a dense ("water-like") medium in the middle and a thin one ("air-like") on the surface.

Re:Isolation, Reflection and Cross-talk (0)

Anonymous Coward | about 5 months ago | (#46489893)

A given design can be frequency limited by propagation delays, as trying to overclock it beyond original design expectations means possibly messing up some timing issue. In general though, delay issues can be designed around and you can make a design that deals with propagation delays (As they actually do in many cases). The limit isn't delay, but heating which scales with frequency from moving charges on and off switches, although can be lessened by making the switches smaller (at potential costs due to leakage current). If you come up with some magic technology that can switch at 1 THz, without producing too much heat, and is actually producible on a commercial scale, than propagation delays won't prevent you from making a much, much faster processor.

Re:Isolation, Reflection and Cross-talk (1)

fractoid (1076465) | about 5 months ago | (#46490749)

Is this still as much the case given the trend towards increasingly parallel multi-core CPUs?

Re:Isolation, Reflection and Cross-talk (2)

Blaskowicz (634489) | about 5 months ago | (#46489519)

Why bother trying to make a CPU with it.
It feels useful to make communication switches, for network cards or to connect a CPU with another CPU, the chipset, a memory pool and so on.

Re:Isolation, Reflection and Cross-talk (2)

fractoid (1076465) | about 5 months ago | (#46490747)

[...] if your new experimental thing isn't at *least* an order of magnitude better than current production, there's little point pursuing it in commercial directions [...]

You have to take into account the potential of the new technology as well. Consider the transition from DC to AC power - initially there wasn't much in it, because voltages were low and transmission distances were short. It was only after the whole electricity industry scaled up that AC really showed its strengths... but the potential was there and so it was a worthwhile investment even early on.

Re:Isolation, Reflection and Cross-talk (1)

Guppy (12314) | about 4 months ago | (#46496091)

You have to take into account the potential of the new technology as well. Consider the transition from DC to AC power - initially there wasn't much in it, because voltages were low and transmission distances were short. It was only after the whole electricity industry scaled up that AC really showed its strengths

And ironically enough, we're now at the point where further developments in technology have meant that DC is now superior for high-power transmission over long distances, thanks to lower power losses and the ability to run high-voltage cables underground/underwater (no capacitive coupling losses).

Re:Isolation, Reflection and Cross-talk (1, Interesting)

Zero__Kelvin (151819) | about 5 months ago | (#46487139)

It works, so presumably they did address those issues ;-)

Also, photons don't have cross-talk. That is a specifically electro-magnetic phenomenon.

Re:Isolation, Reflection and Cross-talk (1)

taktoa (1995544) | about 5 months ago | (#46487479)

> Also, photons don't have cross-talk. That is a specifically electro-magnetic phenomenon.

Photon, n.: a quantum of electromagnetic radiation

Light has cross-talk, because radio has cross-talk, and when you send a signal down a coax cable, you are basically beaming it down a "radio fiber".

Re:Isolation, Reflection and Cross-talk (1)

Snospar (638389) | about 5 months ago | (#46488371)

Where is the "-Not enough Info" moderation when you need it?

I really want to know if photons as quanta don't have crosstalk but this single response on Slashdot has left me begging!

Re:Isolation, Reflection and Cross-talk (2)

Blaskowicz (634489) | about 5 months ago | (#46489481)

Quantum mechanics is weird, I guess a photon crosstalks with itself if it feels like it.

Re:Isolation, Reflection and Cross-talk (1)

Snospar (638389) | about 5 months ago | (#46489513)

Well done, you've summed it up as well as "Tank Fly Boss Walk Jam Nitty Gritty, You're listening to the boy from the big bad city"

This is jam hot.

Good job.

Re:Isolation, Reflection and Cross-talk (0)

Anonymous Coward | about 5 months ago | (#46489915)

Yes, photons and light have cross talk. Just as if your shielding on a cable is too thin you can get signal through it despite being surrounded by a conductor, if the cladding or barrier around a waveguide or fiber is too thin, you will get coupling of light through the barrier.

Re:Isolation, Reflection and Cross-talk (2)

DMUTPeregrine (612791) | about 5 months ago | (#46494131)

"Crosstalk" is a feature of electromagnetic induction: a changing current in one set of wires induces a current in the adjacent set. With light this won't happen at all. You can also have multiple frequency signals across a single wire/fiber optic cable, both will have interference from nearby frequency bands since you can't create ideal filters. These are entirely separate problems, even though they both deal with interference between two (or more) signals.

Re:Isolation, Reflection and Cross-talk (0)

Anonymous Coward | about 5 months ago | (#46494199)

You still get cross talk from parallel optical fibers or waveguides if the boundary between them is too week. There are devices that purposely use these effects, but can be an unwanted issue that has to be dealt with for small scale photonics doing more than just trying to get just a single pipe of light from point A to point B.

Re:Isolation, Reflection and Cross-talk (1)

DMUTPeregrine (612791) | about 4 months ago | (#46495799)

True, light can go through insulation if the opacity is too low, and at small scales the light tunneling across the barrier will become a problem. What you don't get is a direct equivalent to induction that happens in electrical systems, but all the other sources of interference still apply. It's still crosstalk, but not from the cause most often seen in the generally familiar electrical systems.

Re:Isolation, Reflection and Cross-talk (0)

Anonymous Coward | about 5 months ago | (#46487499)

Poorly phrased argument though. Photons are carriers of electromagnetic field.

Re:Isolation, Reflection and Cross-talk (0)

Anonymous Coward | about 5 months ago | (#46487589)

It works, so presumably they did address those issues ;-)

Also, photons don't have cross-talk. That is a specifically electro-magnetic phenomenon.

Photons are a purely electo-magnetic phenomenon. They infact ARE reflections and cross-talk.

Re:Isolation, Reflection and Cross-talk (1)

Jim Sadler (3430529) | about 5 months ago | (#46487737)

Just order a CPU built with this tech now and avoid the rush.

Lost Plane Found! (0)

Anonymous Coward | about 5 months ago | (#46486973)

Here is the scoop - and I know you have been bated by breath, so without further delay,

FOUND!

and

Amelia Erhart said to be doing fine.

haha

Yes, but... (0)

Anonymous Coward | about 5 months ago | (#46487257)

Will it run Crysis?

First sentence of summary is false. (4, Interesting)

smaddox (928261) | about 5 months ago | (#46487505)

Integrated photonics has its place, but it's never going to replace CMOS for computing. Waveguides don't scale like transistors do. If you want to see what integrated photonics is good for, look no further than Infinera. They build photonic integrated circuits for fiber optics communications in 10 years they will own the market for long distance endpoint hardware.

Re:First sentence of summary is false. (1)

Gravis Zero (934156) | about 5 months ago | (#46488667)

Integrated photonics has its place, but it's never going to replace CMOS for computing.

you arent the first to make such a bold assertion. people have said similar things about just about every new technology.

"This 'telephone' has too many shortcomings to be seriously considered as a means of communication. The device is inherently of no value to us." -- Western Union internal memo, 1876.

just sayin

Re:First sentence of summary is false. (1)

Anonymous Coward | about 5 months ago | (#46489725)

I'm going to disagree with you, (and agree with smaddox). Light is not good for computation. Simple put, light doesn't like to interact with itself, so making a transistor or switch is difficult. Sure it can be done, but it inevitably takes a lot of power relative to what it takes make a switch with electronics. What light, however, is excellent for is carrying huge amounts of data down a pipe. That's why IBM and INTEL are interested in integrated photonics.

I'm a researcher in this field and have spoken to experts on Vanadium Dioxide to see if it could be useful for my work. The impression I got was that is that you can switch it in one direction very fast, but the relaxation back is slow. This makes it useless for an optical switch that needs to run at high data rates. If the authors of this work have solved this problem then it's a big deal. Reading the article, though, it sounds like they only talk about switch the VO2 one way. (The article reads like it was intentionally written to obscure this fact,without being outright dishonest).

Re:First sentence of summary is false. (1)

Greyfox (87712) | about 5 months ago | (#46489365)

Indeed! My 70's-era assembly language book speculates that in the future we may have 32 bit processors but 64 bit processors will most likely be too expensive to ever enjoy widespread availability!

Never Replacing CMOS (2)

darenw (74015) | about 5 months ago | (#46489905)

Indeed. For Si-based electronic technology, CMOS or other, we routinely deal with two-digit nanometer scales. 22nm, for example.

For optical technology, structure on that scale has no effect on EM radiation with wavelengths on scales of mm (THz) or microns (IR). This is seriously into UV territory. Bits of matter holding bits of information as a phase changes need to be of a certain size, probably larger than we would like (but I'm not expert on it), for phases to be meaningful.

For a given energy of interaction, massless quanta tend to be more spread out than massive, as a rule of thumb for practical purposes. I think we'll be using electron-oriented information processing technologies for a long time, until someone figures out a way to stabilize muons. Then we can make some really tiny technology.

No general consensus (1)

Anonymous Coward | about 5 months ago | (#46487617)

"There is a general consensus that ultimately photons will replace electrons running through wires in most of our microelectronic devices."

No there isn't.

We know that for silicon CMOS, Moore's law is starting to slow down and further miniaturisation is becoming much more expensive. We know that if the complexity and efficiency of microelectronics is to continue improving at its current or past pace, we'll probably have to move to something other than silicon. There are multiple possibilities, including carbon (graphene or nanotubes), semiconductors other than silicon, titanium dioxide memristors and other more exotic things. Maybe one of these technologies will enable us to push computing closer to its physical limits. Maybe more than one. Maybe none of them will, and eventually we'll just have to be satisfied with gradually refining and optimising silicon CMOS techniques even further. Optical computing has attracted some criticism about its prospects: http://www.nature.com/nphoton/journal/v4/n7/full/nphoton.2010.162.html (sorry for the paywall).

There is no consensus at this point that any particular technology, optical or otherwise, is one of the next major steps in microelectronics.

Re:No general consensus (1)

besalope (1186101) | about 5 months ago | (#46492205)

"There is a general consensus that ultimately photons will replace electrons running through wires in most of our microelectronic devices."

No there isn't.

We know that for silicon CMOS, Moore's law is starting to slow down and further miniaturisation is becoming much more expensive. We know that if the complexity and efficiency of microelectronics is to continue improving at its current or past pace, we'll probably have to move to something other than silicon. There are multiple possibilities, including carbon (graphene or nanotubes), semiconductors other than silicon, titanium dioxide memristors and other more exotic things. Maybe one of these technologies will enable us to push computing closer to its physical limits. Maybe more than one. Maybe none of them will, and eventually we'll just have to be satisfied with gradually refining and optimising silicon CMOS techniques even further. Optical computing has attracted some criticism about its prospects: http://www.nature.com/nphoton/... [nature.com] (sorry for the paywall).

There is no consensus at this point that any particular technology, optical or otherwise, is one of the next major steps in microelectronics.

I think the point that was being made is that optical will eventually replace all electrical connections. It was not saying the only jump to be from Silicon -> Optical, but rather will ultimately be replaced by Optical as a faster medium just like the advances we saw by deploying Fiber Optic cables (and the more recent push for optical-based network switches to replace existing electrical). Realistically the full Optical transition is still years away and you are likely correct that we will move to on of the other transitional architectures that are still electrical-based in the mean time.

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