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Mastering Light
thyristor writes "'Researchers at MIT document the ultimate control over light: a way to shift the frequency of light beams to any desired colour, with near 100 per cent efficiency. This technology could revolutionise a range of fields, from turning heat into light, or even into prized terahertz rays - which hold great promise for medical imaging. It could also make it possible to focus a wide range of frequencies into a narrow band, make devices such as light bulbs and solar cells more efficient, and help to keep optical telecommunications networks moving.' These are probably the most exciting results in photonics in the last decade."
for the next-generation laser pointers!
So, with this, could we look at Ultraviolet radiation with the naked eye (through a converter)? That would be cool! :).
Being able to see infrared radiation would help a lot for playing hide and seek in the dark
Playing pong with lightwaves.
"God fights on the side with the best artillery." - Napoleon, Marshal of France - speaking truth to power
Reading the article it seems that the light frequency is altered for only a short time, the time during which the shock wave passes through the crystal. So I don't think it's some magic filter where you can shine a green light in one end and get red light out the other. In the long term the number of peaks and troughs you put in at one end must equal the number seen at the other, so you can't consistently alter the frequency of a light beam in this way.
IANAP, anyone care to provide more detail than seen in the article? Will the planned demonstration of the work give results observable to the human eye?
-- Ed Avis ed@membled.com
Ok, now, can we control the "shift" from software? which a real explaination for how StarTrek does those "lets generate a xMhz pulse" sorts of things... sending hailing signals over arbitrary frequencies. (like if you had an array of these devices tuned to different freq.). Also, (boy the nerd in me loves this), it generates ideas for reception.. tuning all sorts of frequencies into a standard freq (like for SETI searches....)... wow, neat idea folks.
meh
Joannopolous was also involved in the development of the "perfect" dielectric mirror, which was mentioned here before.
If they could shift heat waves -> light waves, then absorb those with photovoltaic cells, we could harness lots of wasted energy. Almost everything generates wasted heat energy, and isn't heat energy basically the same thing as light waves, just at a different frequency?
I call it a "laser"....
So, does this mean we can make ourselves invisible? If we would make a suit of frequency shifters we could make the visible light turn into radio waves, let them pass through the body, and then change them back into visible light. Of course, it would require huge amounts of energy aswell as precision, so it probablly won't happen anytime soon. Interesting thought, though.
This would actually be pretty cool for the average DJ or night club, since traditional filters are so inefficient, and thus cause you to use higher wattage light, and more heat (and more AC to deal with it). This could make club lighting more attractive, more sophisticated and more varied.
:-)
After all, if science can't help drunk/horny/single people get laid, what good is it?
Tequila: It's not just for breakfast anymore!
Can someone in the audience shed more light into the matter?
No doubt it'll become more transparent as Slashdot editors repost it with increasing frequency.
I flat panel displays will no longer need separate reg, green and blue pixels. They could just have uniform pixels which could produce light in any shade required. Should be good for higher resolution displays, greater colour depth. But might mess up things like sub pixel rendering.
http://grc.com/cleartype.htm
"Taligent is still pure vapor. Maybe they'll be the last who jumps up on Openstep... "
The approach is destructive of the crystal used for filtering the light, although they hope to be able to use sound waves in the future. Due to the distorion of the crystal lattice structure required, even sound waves may wind up breaking the crystal (remember the old memorex commercials with the singer breaking a crystal wine glass). The approach is very interesting, but there still are some serious design issues that they need to address, otherwise, it will be tough to deploy this for applications such as optical repeaters or switches.
Well, with such a frequency translator, we can all imagine all the goodies and baddies that can be made with it. One of them is a cloaking devices, efficient power sources, phase weapons...
Imagine changing harmless light from light bulbs into a focused gamma rays or worse !
I think the summary's mention of "near 100% efficiency" is misleading. It all depends on how wide your definition of the system is. Yes, technically the material itself appears to be highly efficient, but that's discounting all the energy used creating the shockwave necessary to give the material these properties.
A fascinating discovery, yes, but a miraculous way to convert energy to suit our needs it is not.
Have you seen my stapler?
I'm confused. Are you saying that MIT researchers have developed a new "Cyrstal Light" drink mix that changes colors? What flavor is it?
...shift happens!
Q: "Why do sound techs say 'check 1, 2'?"
A: "Cause if they could count any higher they'd be lighting techs."
Not much more information than in the article, but here's the abstract. This is pretty similar to Bragg scattering, which is a well known effect that uses sound waves to upshift the frequency of light. Current Bragg cells are very inefficient and are limited to small shifts in frequency. A high efficiency Bragg cell capable of shifting frequency by a large amount would be extremely interesting.
From Physical Review Letters.
Color of shock waves in photonic crystals
Evan J. Reed, Marin Soljacic, and John D. Joannopoulos
Unexpected and stunning new physical phenomena result when light interacts with a shock wave or shock-like dielectric modulation propagating through a photonic crystal. These new phenomena include the capture of light at the shock wave front and re-emission at a tunable pulse rate and carrier frequency across the bandgap, and bandwidth narrowing as opposed to the ubiquitous bandwidth broadening. To our knowledge, these effects do not occur in any other physical system and are all realizable under experimentally accessible conditions. Furthermore, their generality make them amenable to observation in a variety of time-dependent photonic crystal systems, which has significant technological implications.
Physics, Cosmology and
the light frequency is altered for only a short time
...
... metastable. :-) It doesn't matter, the point is that the wavefronts are recreated continuously, and with sound that doesn't seem all that hard.
The "short time" doesn't really matter, and furthermore looking at a "light beam" as an end-to-end continuous sine wave that you stretch and compress doesn't really help here
Photons last forever (well, until absorbed etc). Once one has escaped from the reflection zone between shockwave fronts, it doesn't wither and die, it's permanently changed to do our beckoning. The fact that its "home of origin" has since moved on isn't really of any further concern. (And notice the difference in velocities between light and shock wavefronts, ie. hare and tortoise, so from the photon's point of view the generator is pretty static.)
Complaining that the shockwave fronts are transitory is like complaining that the metastable states in lasers are, er
"The question of whether machines can think is no more interesting than [] whether submarines can swim" - Dijkstra
- The work is impressive, says materials chemist Michael Sailor at the University of California, San Diego, whose team has developed flexible, biodegradable photonic crystals. He says he now plans to test the phenomenon for himself.
Sounds like they didn't manage to make crystals that actually *last*, and are attempting to sell this bug as a feature.Who says the physical engineering guys can't learn anything from the software guys?
yes, we have no bananas
"We ought to be able to do things that have never been possible before," Joannopoulos. While this is true, its application remains to be seen. I'll wait with held breath for their publication.
On the same note, I wounder wheather this is just the begining of similar earth shattering (whell, light bending in this case) breakthroughs in other fields due to bringing ideas of two different fields together. Most optics people I know would never even consider bringing sound into the picture.
My prediction: new sight and smell techniques will revolutionze the way scientists do research by allowing for instantaneous point density determinations in complex 3-d flows. (Extremely useful!) This will happen when this advacment using sound to modify crystal properties is coupled with a device that picks up minute particle changes over a surface (smell) and correlates the two internally.
-=fshalor
Right now you can buy AOTF cristals. It is a bit similar, but works as a filter (Acousto Optic Tunable Filter). What it does is bend off one specific wavelength of light based on which ultrasound you beam through it. By sandwiching a AOTF crystal between a piezzo and an absorber, you get a filter which you can control with a waveform generator. Brimrose will sell you a spectrometer that can scan 16,000 wavelengths per second for a ridiculously cheap 100,000$. Downturn is it throws all other wavelengths out meaning you still need a 35 Watt halogen lightsource to measure anything. If you could "recuperate" or shift the other wavelengths then you could use LED's as a light source and have a completely solid-state spectrometer with > 30000 H MTBF. You would use less power, produce less heat, make it smaller, send it to Mars,....
10 ?"Hello World" life was simple then
This certainly sounds like an excellent advance in the field.I have been aware of interesting work with shock waves in other materials, for example, to create hydrogen metal, but it wouldn't surprise me if these claimed results were valid.
There are a couple of problems with the article and its claims, however:
I hope for the best, but remain sceptical; let's hope these new shockwave effects become easier to generate and exploit!
I also commented this story here, but I also previously posted another column on this subject. Please read it if you're interested by the photonic revolution.
IAAP (I am a Physicist) and the effect is pretty simple. I think anyone should be able to understand it if it is explained properly.
"Doppler Shift" is a phenomena you are already familiar with. Consider a car honking its horn as he drives by at freeway speeds. As he approaches, the sound is heard at a higher frequency. As he passes by, the frequency shifts, and as he is leaving, the frequency is lower than normal.
Light is like sound in that it is a wave and has a frequency. Let's examine light from high to low frequencies. X-Rays are light at extremely high frequencies. Ultra-Violet light is just above the visible light range. Then we get into the rainbow - blue, then green, then red. Next is infra-red light -- light just below red in frequency. Travelling farther down, we start to reach the radio band. Below that, the frequencies are so low that it no longer is light anymore, but more like a slowly shifting magnetic or electric field.
The Doppler effect works for light as well. The problem is you or the object emanating the light has to be travelling near light speeds to see any noticeable effect. We call this "redshift" in astronomy, because stars seem to be travelling away from us, and so the light emanating from them is lower in frequency (more red). Certainly, attaining near-light-speeds is dangerous and difficult. We're not talking "bullet" fast, we are talking "cosmic ray" fast.
However, there is an oh-so-tiny Doppler shift when *any* motion is involved with light. When your friend walks towards you, the light bouncing off of him is slightly more blue. When he walks away, it is slightly more red. Good luck actually detecting this, however.
Photonic crystals have the strange property of behaving like a piece of glass at one moment, and a mirror the next, depending on how much pressure is applied where.
So, using a proper push on the crystal, it is possible to set up a travelling hall of mirrors. The light appears to be slightly shifted due to the Doppler effect to the mirror, so when it is reflected, the light is shifted, by an oh-so-tiny amount. Multiply that shift by a kazillion reflections, which is quite possible if you make the hall of mirrors very tiny (think atomic scale), and you can control light to almost any frequency, high or low, depending on how you set up the mirrors.
So, the net effect is light goes in at one frequency, and comes out the other end at another, without expending hardly any energy to get it done.
The engineering challenge is configuring the crystal so that it can withstand the forces that need to be applied, and applying the forces in a controllable way. Right now they are doing tests with bullets and crystals, because they only need to record data for the instant that the shock waves are travelling through the crystal, and they don't mind using a cheap, destructive method. In the future, they will probably use sound waves to control the crystal. But how they configure this is left to the imagination.
The applications are numerous, and some of them are listed in the article. Needless to say, if we want to use light to transmit data, the more control we have over the light, the more effective we can be in transmitting that data. Also, doctors will be happy because we can now easily exploit the Terahertz range for X-ray type applications.
The radical sect of Islam would either see you dead or "reverted" to Islam.
Thank god... now just before Zephran Cochran launches, we'll have the frequency shifting lasers we need to stop the Borg without any help.
This is certainly an interesting result, but its heavily hyped as well.
First of all, there are many many ways to shift the frequency of light, both up and down in frequency, with both linear and nonlinear means, - from the Raman effect in optical fibers (scattering off vibrations of silica molecules) to Optical Parametric Oscillators (nonlinear wave mixing), supercontinuum generation (using a multitude of nonlinear effects to generate broad bandwidth from a single laser) to simple OEO conversion (detect your light with a photodiode and use it to drive another laser at a different wavelength. Contrary to what this article implies, these effects work at modest power levels in todays optical fibers, and many are highly efficient, and work over extremely broad bandwidths. For example, supercontinuum generation can generate light sources with bandwidth covering the entire visible, UV and IR spectrum in one source! If you want to talk about bulk optic techniques for wavelength conversion, the list is even longer.
Now think a minute about what these guys are proposing. They have to shock the crystal. Initial experiments will destroy the sample. Maybe they can refine the technique down the line to nondestructively shock the sample, maybe they can't. Certainly, infinite bandwidth won't be available, since the amount of wavelength shift will depend on the amount of shock. A single shot technique for wavelength shifting, while interesting, isn't all that useful practically.
Second, they are using a shock, so conversion of CW light is out of the question, only pulses can be converted here, or you risk a time dependent wavelength shift, as your shock dies out.
Finally, claims of a completely new physical effect seem somewhat overblown. It is an interesting idea, but Doppler shifting off acoustic shocks, and photonic crystals are well known. Marrying the two together and finding a stable regime of operation is novel, but not quite the same as discovering a new physical princple like relativity or quantum mechanics, for example.
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The article mentions an interesting fact that the researchers are using bullets instead of sound shock waves. "That will, of course, destroy the crystal"... I can just imagine what goes on in that lab:
"Allrighty, George, it's your turn with the gun."
"But Bill, you know George can't hit the broad side of a barn!"
"Nonsense, my dear fellow. We need to produce some blue light soon, and that calls for a once-in-a-blue-moon event. Come on, George; ready... aim... fire! Take the safety off first, George. Gees... you call yourself a scientist? Ready... aim... fire!"
"Oh, no, not my brand new spectrometer!..."
"Look... Blue light! Woooohoooo!"
how cool - finally we can have computers full of flashing lights Just like in the movies...
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The radiation selectivity property was discovered by observing the phenomenon of Cherenkov radiation inside the photonic crystal.
u o_science_2003.pdf]
For further more detailed technical information, a PDF of the paper is here [http://physics.ucsd.edu/~drs/publications/2003/l
Photonic crystals fall under a broader family of materials called "metamaterials".
Future research note: Software-programmable metamaterials will create wonderfully exotic applications.
Cheers
Andrew
IANAP[hysicist], and so I have some questions about this process.
What I know:
So, when light is converted to a higher frequency (shorter wavelength) where does the necessary energy come from? The shockwave? What about when it is converted to a lower frequency (longer wavelength)? Where does the excess energy go? If the conversion really is 100% efficient (I'm a bit skeptical of that claim), then just imagine the solar panels we could have; sucking up all the UV raining down on us and emitting a soft red glow.
Fascinating stuff. I've got to study more optics and electromagnetic physics.
But they do occur with alarming frequency.
"He who laughs last, didn't get the joke."-Cap
Sure, if you shift the frequency down far enough. Problem is, you would only be able to see the world in x-rays. And lemme tell you, it's pretty dark at that end of the spectrum. The atmosphere filters out most of the higher-range radiation (a few dozen kilometers of air is about as effective as 8 centimeters of solid lead), which is why x-ray machines are all about the generation of radiation; seeing it on film the easy part.
If you want comic-book style x-ray specs, then we're talking about short microwave and far-infrared radiation. Then you just shift the radiation back up into the visible spectrum and you can see through clothes, flesh, fairly un-dense stuff like that.
Dyolf Knip