Nano-Scale Optical Co-Axial Cables Announced

toybuilder writes "Reuters reports that scientists have published their work on nano-scale optical coax in the most recent issue of Applied Physics Letters. The coax cable is only about 300nm wide, and is able to transmit optical signals using a carbon center conductor, transmitting light at about 90% the speed of light."

Re:huh?

[mandelbr0t]

The physics constant c refers to the speed of light in a vacuum. Read here [rpi.edu] to find out why this statement isn't stupid.

mandelbr0t

Re:90% of the speed of light....

[medge_42]

I should mention that that was going through a block of sodium at -272C (near absolute zero)

Re:WTF?

[Anonymous Coward]

You have faith in the peer reviewed physics journal? You must not know any of the peers, or have any insight into the review process. Trust me, its a mess. Although I am not a physicist myself, my friends who are complain to no end at the state of affairs with the journals. Its not that everything published is wrong, its just most of it is very, very difficult to review and very very little of it is worth reading. Its never wrong to ask stupid questions, or compare new discoveries to existing models of thought on a discussion forum. Of course, in this case it answers the question in the article, but it should have been in the summary.

Thosands of times faster than electronics?

[JesseL]

From TFA:

"It's not quite the speed of light, but it's probably 90 percent the speed of light. That's still thousands of times faster than electronics," Naughton said in an interview.

It was my understanding that electric fields propagate through copper at about 1/3 C.

thickness is the key issue

[rjdegraaf]

The 300nm wide fiber is the key issue.

The thinner the fiber, the less the digital light pulses are spread (due to reflections on the fiber shell) per unit distance, the more information can be sent through per unit time.

Thinner means more bandwidth.

Re:WTF?

[kebes]

Well put. The original scientific article in question is this one:

Rybczynski, J.; Kempa, K.; Herczynski, A.; Wang, Y.; Naughton, M. J.; Ren, Z. F.; Huang, Z. P.; Cai, D.; Giersig, M. "Subwavelength waveguide for visible light" Applied Physics Letters 2007, 90, (2), 021104. (doi: 10.1063/1.2430400).

The paper is here [aip.org], although only subscribers can read the fulltext. The abstract says this:

The authors demonstrate transmission of visible light through metallic coaxial nanostructures many wavelengths in length, with coaxial electrode spacing much less than a wavelength. Since the light frequency is well below the plasma resonance in the metal of the electrodes, the propagating mode reduces to the well-known transverse electromagnetic mode of a coaxial waveguide. They have thus achieved a faithful analog of the conventional coaxial cable for visible light. ©2007 American Institute of Physics

These are extremely small structures and this leads to an interaction between the light (which is an electromagnetic wave of course) that is essentially identical to when radiofrequency EM radiation propagates down a normal (macroscopic) coax cable. Specifically, in the introduction they say:

In this work, we show experimentally that a nanoscopic analog of the conventional coaxial cable, with properly chosen metals for the electrodes and proper electrode dimensions, indeed retains approximately all of the above properties of its conventional macroscale cousin.

Then they go through the details. Their device uses a multiwall carbon-nanotube (MWCNT) as the center conductor (it is a 'metallic' CNT). The MWCNT is embedded in aluminum oxide, which acts as the optically transparent 'dielectric'. The outer wrapping electrode is made of chromium.

The mere creation of these nano-sized devices is quite an accomplishment. The fact that they've demonstrated successful transmission of light through these sub-wavelength sized devices is even more impressive. I can imagine a wide range of applications in nano-scale imaging (imagine a massive array of NSOMs [wikipedia.org]), lithography, or even optical computing.

Re:Thosands of times faster than electronics?

[KokorHekkus]

I thought it was a bit higher than that (still not 90% though). Did some digging and wikipedia came up with that the velocity of propagation was about .79 for a coax cable according to it. Checked a supplier of coax cables and they quoted velocity of propagation at .66 C to .84 C (latter for 1.13 mm copper KTV cable with PE insulation)

Source: http://en.wikipedia.org/wiki/Velocity_of_propagati on [wikipedia.org]

Re:WTF?

[MustardMan]

Yes, I DO have faith in the peer review process. It's far from perfect, but it's not as bad as you make it out to be. The thing you need to know is, a lot of physicists, and scientists in general (myself included) can be really anally retentive bastards. I one got blasted for fifteen minutes over my use of the phrase "high reynolds number" when the colleague in question believed "moderate" was the appropriate adjective and "high" was misleading. These are the types of errors that get physicists steaming, and with good reason - physics is perhaps the most rigorous of the sciences, and you have to be damn careful about how you word things. People will complain, loudly, about very minor issues. Many scientists strive for absolute perfection, and fixate on the negatives in an attempt to make the process better. There's nothing wrong with this, but it's useful to keep in mind when you form opinions about the peer review process based on your friends' complaints.

When people bitch about physics journals, in my experience it's been mainly for two common reasons:
1.) Drawing large, over-arching conclusions without enough evidence to support it. This is in no way saying the bulk of the work is invalid, just that the authors got a little greedy when writing the conclusions.
2.) Disagreement with the underlying assumptions that make up the paper. This one is trickier, but again it doesn't immediately invalidate the work, just questions how relevant the results are.

In either case, the peer review process, by people well-versed in the field, is a whole HELL of a lot more trustworthy than the slashdot peanut-gallery. The OP was full of crap, and others have gone into great detail to explain why he/she is full of crap. I was merely pointing out that the knee-jerk slashdot "post early, post often" karma whoring competitions lead to a whole lot of dumbass assertions without any firm understanding of the actual facts of the discussion.

Re:I have problems with regular coax...

[halftrack]

do we really have problem with interference in fiber where we have to use coaxial cable???

Most (all?) fiber optical cables have a co-axial design. Simplified; there is a core and a cladding, with the cladding having a lower refractive index than the core; thus creating total reflection (multimode fibers.) Now the cladding could be the air surrounding the cable, but it's probably not, thus as you see the co-axial design is a reasonable one. (Though you could probably get a away with some off axis designs, at least for multimode fibers.)

Wikipedia on fiber optics [wikipedia.org]

As for the GP, he might be joking but that is actually a serious concern. To get the correct electromagnetic modes in the fiber you need to align your fiber with your source carefully. obviously this isn't easy when for instance connecting this 300 nm fiber to some chip ... probably mostly useful for integrated stuff. (NIDNRTFA)

Re:Sorry to be picky but

[Cyrom]

When not qualified the term "speed of light", to the majority of the population (except maybe a few who think they are clever for pointing out the lack of said qualification), means the speed of light in a vacuum. When one is referring to the speed of light through some other medium it is usually stated as such.

Re:Coax is silly for optical

[fluffy99]

You obviously didn't read the entire article. The whole point is that they are shoving something with a wavelength of 375 nm down a 300 nm pipe. They explained that this is the exact same issue with shoving RF down a coax (ie 1-meter wavelengths down a 1/4" coax).

Re:90% of the speed of light....

[PhysicsPhil]

Of course, if you REALLY want to be pedantic, the speed of light in a vacuum is measured, and the meter is defined as being the distance light travels in 1/299792458th of a second.

While this is Slashdot, we still encourage pedantic comments to be correct. :)

Your definition of the metre is correct, but you may notice that it fixes the speed of light at precisely 299792458 m/s, with no room for measurement. What you actually do in modern science is measure a second with a very precise clock, and calibrate your meter bar appropriately. Any errors you make are in the length of the metre, not the speed of light.

It didn't always used to be this way; for about eighty years the meter was defined in terms of atomic transition lines, so that the speed of light was the measured value. In 1983, however, timekeeping was accurate enough that the definition of the metre changed over so that the metre was a derived quantity.

c the constant

[H0D_G]

Actually, the speed of light in a vacuum is not constant at all, according to several current theories. Professor R.T. Cahill's process physics theory(i mention this one, cause i've had some lectures on it, but there are others) states that the speed of light is actually inconstant, and depends on the flow of space around it. I don't claim to understand it, being a humble chemist, but it's interesting stuff http://www.arxiv.org/abs/gr-qc/0203015 [arxiv.org] for a cahill paper