Mastering Light 421
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."
Skimpy article. (Score:2, Funny)
I can't wait... (Score:4, Funny)
Re:I can't wait... (Score:5, Funny)
Re:I can't wait... (Score:5, Funny)
[sound of tumbleweed]
I'll get my coat.
Re:I can't wait... (Score:5, Funny)
Re:I can't wait... (Score:4, Funny)
Re:I can't wait... (Score:5, Funny)
Re:I can't wait... (Score:5, Funny)
Re:I can't wait... (Score:5, Funny)
Re:I can't wait... (Score:5, Funny)
Re:I can't wait... (Score:4, Funny)
Bohring maybe, but... (Score:4, Funny)
Can anyone say cloaking devices ? (Score:5, Interesting)
Imagine changing harmless light from light bulbs into a focused gamma rays or worse !
Re:Can anyone say cloaking devices ? (Score:3, Interesting)
Re:Can anyone say cloaking devices ? (Score:3, Interesting)
Re:I can't wait... (Score:2, Insightful)
Re:I can't wait... (Score:3, Funny)
See outside the bubble? (Score:4, Interesting)
Being able to see infrared radiation would help a lot for playing hide and seek in the dark
Re:See outside the bubble? (Score:2, Insightful)
Re:See outside the bubble? (Score:3, Interesting)
If instead there was a filter that converted infrared light to visible light completely, then the sensors would be much much more sensitive to it
Re:See outside the bubble? (Score:3, Informative)
Re:See outside the bubble? (Score:3, Informative)
Re:See outside the bubble? (Score:5, Interesting)
I interpreted the article to say that they shift light like a audio pitch shifter may change the key of a song to be more conducive to a singers natural range. Cooler objects would be, say, red and warmer objects would look oranger.
If this has the efficiency they claim, you could get more visible light out of a standard light bulb. This would save energy.
Re:See outside the bubble? (Score:3, Informative)
I think you are confusing the infrared spectrum with the concept of color temperature. The idea of color temperature arises naturally from blackbody radiation--as a blackbody radiator gets hotter, its peak emission wavelength gets shorter. If it's hot enough, it picks up a distinctive color (for example, blackbodies look red around 3000 Kelvin, IIRC, and yellow around 6000 Kelvin). It
Re:See outside the bubble? (Score:2)
Re:See outside the bubble? (Score:5, Informative)
converters UV->visible do also exist and are commercially available, they are not as common because they do not have so many applications (one of them is to detect corona discharge in high voltage applications, power lines). They use a stack of a photocathode (UV light->electrons), Micro Channel Plates (amplification) and a Phosphor Screen (electrons->visible light).
Re:See outside the bubble? (Score:4, Interesting)
that would truly be staggering... It could change everything...
How about the possible implications in fusion or anti-matter research? bumping up the frequency of light enough to have the frequency of the light alone manipulate the atoms...
or even wilder... zero point fields? those theories are out there too... -- being able to harness EM fields so high frequency... we cant' detect 'em.. though we could tap into 'em by scaling 'em down to such a degree where they're useful...
truly exciting..
More to the point... (Score:3, Interesting)
Re:More to the point... (Score:4, Interesting)
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.
Summary Of Technique (Score:3, Funny)
You forgot the bullets... (Score:5, Funny)
"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!"
For how long? (Score:4, Interesting)
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?
Re:For how long? (Score:2, Interesting)
The magic filter is exactly what the article suggests, but I can't see how it works.
It seems to suggest that "Because the shock wave is moving through the crystal, the light gets Doppler shifted each time it bounces off it" But surely it gets shifted up when it hits the approaching wave and down again when it hits the retreating one. It would have to continously bounce off approaching or retreating waves in order to get shifted up or down. Maybe they use some kind of concentric shockwaves, but even then it
Re:For how long? (Score:5, Interesting)
Jeroen
Re:For how long? (Score:3, Interesting)
Assuming the pressure wave is reversed (ie the crystal doesn't explode), then yes the light will be doppler shifted the other way if it hits the rebounding boundary.
This could be taken care of by careful timing, although it might limit the range of practical shifts.
But who cares about practice! I was always a theoretician - didn't like getting my hands dirty with real photons ;-)
Re:For how long? (Score:5, Interesting)
- Generate low-frequency (LF) pulse travelling into crystal.
- Apply shock wave to turn crystal into frequency shifter.
- Wait until LF pulse is shifted to higher frequency and emitted from crystal.
- Allow time for crystal to relax to original properties by allowing the shock wave to dissipate.
- Repeat for as long as necessary/desired.
Now, this may or may not create any really usable stream of pulses, but I believe that you would be able to shine a (pulsed) red light in and get a (pulsed) blue light out. Whether the pulsing could be controlled sufficiently to prove useful in optical switching or other applications is yet to be shown.As for the number of wavecycles being equal, I wonder if this is already observed. It would make sense (if the number of wavecycles is conserved) that the resulting higher frequency pulse would be shorter in duration than the incoming lower frequency pulse, due to the relation among the speed of light/frequency of light/duration of pulse.
Re:For how long? (Score:3, Interesting)
No, the shock wave passing through the crystal causes the "hall of mirrors" effect with a moving mirror (the compressed/uncompressed interface) which produces a Doppler shift.
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
That's exactly what it is.
In the long term the number of pea
Re:For how long? (Score:2)
Since most light sources are periodic (pulses). (Tubes/TVs/Monitors/Plasma Displays/fluorescent), perhaps there is (some) posibility this could be applied.
Like many great discoveries, we do not fully see the benifits immediately.
Re:For how long? (Score:5, Interesting)
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 you put through another shock wave and another and another and another...
You will get the same number of peaks and troughs out, but those that have bounced back and forth a bit (and thus got Doppler shifted) will come out later, having travelled further, and shifted. This technique stretches the light pulse.
So, (asciiart time!) you could put in pulses of green and get out continuous red:
S S S S
gggg gggg gggg gggg
rrrrrrrrrrrrrrrrrrrrrrrr
[View it in a fixed-width font, it'll make sense I promise]
Each green pulse g has been stretched by the shockwave sent at each S and turned to red light r, filling the time for pulse + gap.
Justin.
Re:For how long? (Score:3, Interesting)
Doesn't matter, it's more than long enough (Score:5, Interesting)
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
IAAP -- Here it is in plain English. (Score:5, Informative)
"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.
Slight correction. (Score:3, Interesting)
Don't confuse cosmological redshift with Doppler-induced redshift. In astronomy, the redshift that's talked about is typically not due to the literal motion of the star. It really arises from the space between Earth and the star under observation expanding. It's really quite a neat little effect. I'm not going into the detail here, but I'd recommend reading a little about it.
Anyway, because the redshift comes from the space itself expanding, it's proportional (I
Re:IAAP -- Here it is in plain English. (Score:5, Informative)
In the same way, the walls of the crystal that the light is bouncing off of are vibrating back and forth. If the vibrations are timed such that a wall is always moving towards or away from an incident photon when it strikes the photons will always be gaining or losing wavelength due to the doppler shift.
Re:For how long? (Score:5, Informative)
Re:Mod this idiot down! (Score:3, Insightful)
Michael Jackson (Score:4, Funny)
One of the first uses of this would be to make Michael Jackson even more white.
unexpected? (Score:2)
Yay for guess and check!
Re:unexpected? (Score:5, Informative)
Star Trek has been completed! (Score:3, Interesting)
Re:Star Trek has been completed! (Score:4, Funny)
Star Trek will NOT be complete until we have discovered how the Klingons and Romulans make their CLOAKING DEVICES. And while we're at it, I wish Zephram Cochran would hurry up and be born so he can invent the Warp Drive. You know, I thought we almost had the Warp Drive with Asymetical Capacitors, but others here on Slashdot have pointed out that they don't work in a vacuum. One more thing, we need Transporters to beam down to other planets from orbit. We're a long way from Star Trek.
Innovative group (Score:5, Informative)
Heat - energy (Score:4, Interesting)
Re:Heat - energy (Score:5, Informative)
Heat comes in two flavors - radiated light waves and random molecular motion. The second kind is irrelevant to this discussion. As far as the first kind goes, you can't magically make that radiated light have more energy by converting it up to a higher frequency.
The laws of conversation of energy and thermodynamics would like to have a little word with you out back...
Re:Heat - energy (Score:3, Funny)
Three consecutive days with temperatures of 90 degrees (F) or above.
Re:Heat - energy (Score:3, Interesting)
There are two ways things radiate heat, as another poster points out; One is by losing its heat energy to neighboring substances, thus exciting them and becoming less excited. The other is through near-infrared radiation.
Things which absorb IR are heated by it, and things which reflect IR are not. Most things are somewhere in b
All one frequency? (Score:3, Funny)
dilithium anyone? (Score:2)
"Captain, I think we can modulate the dilithium crystal resonance and redirect the warp increase to the forward sensor array!"
In other words, it sounds brilliant without actually making any sense.
Invisibility possible now? (Score:3, Interesting)
Re:Invisibility possible now? (Score:3, Interesting)
The difficulty would be to get the shock waves going in the direction of light for all directions or light!
That doesn't mean it can't/won't be managed though.
Justin.
Re:Invisibility possible now? (Score:2)
I can imagine (Score:2, Interesting)
DJs! (Score:5, Insightful)
After all, if science can't help drunk/horny/single people get laid, what good is it?
Re:DJs! (Score:5, Funny)
Only on Slashdot would this be moderated "insightful" rather than "funny".
Now when I put on my photonic crystal flame suit.. (Score:2)
new technique for displays? (Score:5, Insightful)
http://grc.com/cleartype.htm
Re:new technique for displays? (Score:5, Interesting)
Re:new technique for displays? (Score:4, Interesting)
Ummm... How would you get white (red, green, and blue at the same time)? I suppose that you COULD rapidly switch between multiple frequencies to get a simulated white, but the article did not explain how much control you could get over the process... Perhaps a single crystal would only provide a fixed shift (red->blue), and if you wanted red->green, you use a different crystal.
Also, each pixel would need its own crystal and "hammer" (probably a piezo element). This would probably be even more expensive than current flat-screen televisions.
Just one more note -- if you have little crystals being hit at 60Hz (assuming a progressive scan display), that sucker would humm like crazy!
Photonic Condensator? (Score:2, Insightful)
Could this be the starting point for some sort of photonic condensator? Maybe, this could in turn be used for building a volatile photonic memory system?
That would mean a great leap in photo-electronic computer systems, since normally, a lot o
The technology smashes the crystal (Score:5, Informative)
Re:The technology smashes the crystal (Score:3, Informative)
That's only a serious problem if they hit the resonant frequency of the crystal, or a multiple thereof. As long as they avoid this, it would have to be one serious sound wave, in which case a greater problem might be the neighbours :-)
Efficiency (Score:5, Insightful)
A fascinating discovery, yes, but a miraculous way to convert energy to suit our needs it is not.
Re:Efficiency (Score:3, Informative)
Optical conversion efficiency is what is important, for example, in wavelength conversion for data transmission. You don't want to lose signal power.
New drink mix??? (Score:4, Funny)
What's the range of effect? (Score:3, Insightful)
Could this effect mean one could upshift radio waves to hard xrays? Or microwaves to gamma rays? The idea that this can be done with nearly 100% efficiency is the biggest wow-factor and seems like it should be violating the 2nd Law of Thermodynamics.
Re:What's the range of effect? (Score:2, Informative)
Re:What's the range of effect? (Score:3, Interesting)
Lawrence Livermore and bullets (Score:2)
You know what they say about the EM spectrum... (Score:3, Funny)
No article up yet, but here's the abstract (Score:5, Informative)
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. [aps.org]
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.
Cool application! (Score:3, Interesting)
Or perhaps even infrared/heat?
Cool glasses that make you see in the dark? (military applications?)
Whee!
Biodegradable? (Score:3, Funny)
- 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?
RE: The future of...*Everything*!?! (Score:3, Interesting)
"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.
Does this mean (Score:2, Funny)
Re:Does this mean (Score:2)
You could also try throwing it very hard....
Jeroen
High-efficiency automobile lighting? (Score:3, Insightful)
This research could point the way for automotive lighting systems that are far more efficient than today's lights but use a tiny fraction of its power.
Already, we've seen LED taillights on a number of cars such as the Nissan Skyline (as the Infiniti G35 is known in most of the world). This research could lead to LED-based automobile headlights that are just as bright as the high-intensity discharge (HID) xenon headlights found on more expensive automobiles but doesn't need the expensive power generating system HID headlights now need and uses a tiny fraction of the power needed for regular headlights. Other lighting systems such as fog lights could benefit from these new technologies, too.
Peer Review? (Score:5, Informative)
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!
Is the Photonic Revolution Coming? (Score:5, Informative)
Just in time... (Score:5, Funny)
Take it easy on the hype there! (Score:5, Informative)
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.
Better solar power generators (Score:3, Interesting)
This would make microwave beaming satellites highly efficient. The current idea was to have huge solar arrays which would of course alter the look of the sky during the day or night. These would convert some of the light into energy and probably reflect the rest of lose it as heat. The elctricity generated would produce a microwave signal which would be beamed down to a ground station and converted back into electricity. With this new technology, they could have far smaller arrays which convert the light directly into microwaves and transmit, eliminating the overhead of going from light->electricity->microwaves->electrici ty on the ground.
Instead you would have light->microwaves->electricity on the ground.
And you wouldn't need a mile long array of cells to collect enough power to make it worthwhile because your effeciency would be extremely high.
Actual Phenomenon (Cherenkov) and Research Paper (Score:3, Informative)
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
Most famous words in science (Score:3, Interesting)
Something is bugging me (Score:5, Interesting)
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.
Neat! (Score:3, Funny)
Who says science isn't fun?
Efficiency Near 100% ? (Score:3, Interesting)
Of course I haven't seen their simulations, but where does this "near 100%" figure come from? The first test is going to use a bullet (!) and they are projecting that a more refined version will use sound waves. Something has to produce those sound waves, and the waves have to be powerful enough to alter the characteristics of the crystal.
Now I understand that in theory a light wave at a given frequency could transform to a higher frequency and lower intensity (conservation of energy is not violated), but that's analogous to changing the gear ratio on a motor. A gear system always introduces some loss.
Now, given that any practical implementation of this will require a wave generator that's likely to make some noise, I don't see it ending up in lightbulbs or solar cells. If you want to get more light to a solar cell, focusing a mirror on it and keeping it cool is probably more practical.
However, the medical imaging tech sounds like a great application. Noise from medical scanners is an acceptable part of that experience.
Re:Rather skimpy article. (Score:3, Funny)
No doubt it'll become more transparent as Slashdot editors repost it with increasing frequency.
Re:Rather skimpy article. (Score:5, Informative)
Re:question (Score:2)
They are shifting the frequency (the color) of light not its path.
Jeroen
Re:CPU cooling? (Score:4, Interesting)