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."
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
question (Score:0, Interesting)
But honestly, do they have the ability to actually shift the light, almost like a curve effect to the beam. Cause I know not too long ago
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?
Star Trek has been completed! (Score:3, Interesting)
Heat - energy (Score:4, Interesting)
Invisibility possible now? (Score:3, Interesting)
I can imagine (Score:2, Interesting)
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 would have to pass through retreating waves unaffected in order to hit another approaching one.
I also can't get my head round how you would shift the frequency without moving the source at near to the speed of light. Anyone got any ideas?
Can anyone say cloaking devices ? (Score:5, Interesting)
Imagine changing harmless light from light bulbs into a focused gamma rays or worse !
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 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.
Number is not frequency: you could still see the same number at a lower or higher frequency, the total observation would just take a longer or shorter time. The red shift of the light of galaxies apparently receding from us at a high fraction of c is a consistent feature, caused by exactly the same Doppler effect.
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:5, Interesting)
Jeroen
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
Cool application! (Score:3, Interesting)
Or perhaps even infrared/heat?
Cool glasses that make you see in the dark? (military applications?)
Whee!
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.
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:new technique for displays? (Score:5, Interesting)
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 and viewing normal things with your eyeball would be very practical.
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!
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 ;-)
Oh, and the shift will occur whatever the speed is, it'll just be a smaller shift for a slower boundary.
Justin.
Re:For how long? (Score:3, Interesting)
Re:CPU cooling? (Score:4, Interesting)
Slight correction. (Score:3, Interesting)
Anyway, because the redshift comes from the space itself expanding, it's proportional (I think it's a linear effect, I don't remember too well) to the distance between you and the object under observation. Yes, there is some Doppler style redshift, but that is not what's generally meant when an astronomer says "redshift". Also, cosmologists use redshift (z) as their primary variable in many equations. Most cosmologists measure distance in redshift, instead of cgs or mks length units.
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.
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.
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..
Re:Can anyone say cloaking devices ? (Score:3, Interesting)
Re:Can anyone say cloaking devices ? (Score:3, Interesting)
Re:See outside the bubble? (Score:1, Interesting)
More to the point... (Score:3, Interesting)
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.
6th Column (Score:2, Interesting)
Seems like there was another Heinlein story that used a light wavelength shifter as an energy resource - one that ultimately powered moving sidewalks...anyone remember the title of that story?
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.
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: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 between, reflecting a percentage of IR. In a vacuum you can't cool by convection for example so you paint one side reflective and insulated and the other side black and noninsulated and control temperature by rotating; The black side will radiate in the near-infrared and provide (slow) cooling. I have no idea why black surfaces radiate more heat, surely someone will explain it to me someday. Or soon.
So heat itself cannot be converted. IR can be converted, but most loss of heat in terrestrial (or other environmental) systems is not due to infrared radiation. Heat energy is essentially kinetic energy on a very fine scale, whereas developing energy from light involves photons knocking around electrons.
Re:What's the range of effect? (Score:3, Interesting)
Re:Can anyone say cloaking devices ? (Score:2, Interesting)
The way I understand this system, it would be like tossing a pingpong ball into a match with a couple of mad pingpong players. The paddles, moving back and forth as a well-timed shockwave would, add energy to the ball and it is shot out of the system with higher energy than it was tossed in.
Is this analogy accurate?