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Science Technology

Mastering Light 421

Posted by michael
from the heel dept.
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."
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Mastering Light

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  • Will someone else shed more light into the matter???
  • by WormholeFiend (674934) on Thursday May 22, 2003 @09:09AM (#6014441)
    for the next-generation laser pointers!
  • by Anonymous Coward on Thursday May 22, 2003 @09:11AM (#6014457)
    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 :).
    • have you ever looked through a Hoya R72 infrared filter, or a B+W 58ES 403 ultraviolet-transmitting filter?
      • AFAIK, infrared filters simply block all visible light, and assume that the film/CCD/cornea behind it will be slightly sensitive to infrared light. This assumption is true, but (other than infrared film) those sensors aren't very sensitive to infrared so the image will be very dim, so you either have to look at the sun, or use long exposure times for the camera.

        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

        • by kevlar (13509)
          Actually, this isn't true. IR Filters FILTER Infrared light, preventing it from impacting the underlying CCD. All CCD and CMOS cameras have them. When removed, you can pick up an enormous amount of noise, including clicks from your remote control, which easily overflow the hit count on the chip and spam the resulting photo.
    • If you're looking through a converter then you're not looking with the naked eye.
    • by esonik (222874) on Thursday May 22, 2003 @10:32AM (#6014947)
      converters IR->visible are widely known: night vision goggles.

      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).
    • by prmths (325452) <prmths@noSpaM.f00.org> on Thursday May 22, 2003 @10:58AM (#6015104) Homepage
      not just that.. i BET that with this technology.. MAYBE ... JUST MAYBE they'll find a way to prove the unified force theory... if they can shift an EM feild enough so that it behaves like gravity, or vica-versa (assuming the theory is true)
      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)

      by kinnell (607819)
      Does this mean we'll finally be able to get X-Ray specs?
      • by Dyolf Knip (165446) on Thursday May 22, 2003 @01:47PM (#6016664) Homepage
        Does this mean we'll finally be able to get X-Ray specs?

        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.

  • by N8F8 (4562) on Thursday May 22, 2003 @09:12AM (#6014464)
    Playing pong with lightwaves.
    • by Chemisor (97276) on Thursday May 22, 2003 @10:19AM (#6014870)
      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!"
  • For how long? (Score:4, Interesting)

    by Ed Avis (5917) <ed@membled.com> on Thursday May 22, 2003 @09:12AM (#6014468) Homepage
    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?
    • Re:For how long? (Score:2, Interesting)

      by Becquerel (645675)

      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)

        by pe1rxq (141710) on Thursday May 22, 2003 @09:36AM (#6014594) Homepage Journal
        The trick is to let it bounce of a shock wave, not a continous wave. You simple let the light escape when it has the right frequency. As long as its gone while the shockwave is still going in one direction it will work.

        Jeroen
      • Re:For how long? (Score:3, Interesting)

        by aug24 (38229)
        Firstly, a photon will bounce off the material boundaries within the crystal forever unless it has the frequency we want.

        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)

      by IsaacW (543020) <isaac.waldron@gma3.14il.com minus pi> on Thursday May 22, 2003 @09:30AM (#6014562) Homepage
      The article states that shifting red light up in frequency to blue light takes about 10,000 reflections (about 0.1 nanoseconds). I think that you could shift a pulsed light source in this manner:
      1. Generate low-frequency (LF) pulse travelling into crystal.
      2. Apply shock wave to turn crystal into frequency shifter.
      3. Wait until LF pulse is shifted to higher frequency and emitted from crystal.
      4. Allow time for crystal to relax to original properties by allowing the shock wave to dissipate.
      5. 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)

      by Polaris (9232)
      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
      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
    • Unless you have pulsed light input which is in sync with the shock wave passing through the crystal?

      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)

      by aug24 (38229) on Thursday May 22, 2003 @09:36AM (#6014593) Homepage
      IANAP, but I am a Physics grad, so...

      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)

        by Rich0 (548339)
        I wonder if large frequency shifts towards higher frequencies would require a substantial energy input to power the shock wave? If you put in 50 photons at frequency x and get out 50 at freq x+n, you have to put energy into the system. Likewise if you downshift in frequency you must be releasing energy - perhaps the shock wave could become self-sustaining? This still could be useful for power-generation - most photovoltaics have optimum absorbtion frequencies, and a lot of work probably goes into broaden
    • by Morgaine (4316) on Thursday May 22, 2003 @09:38AM (#6014604)
      the light frequency is altered for only a short time

      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 ... metastable. :-) It doesn't matter, the point is that the wavefronts are recreated continuously, and with sound that doesn't seem all that hard.
    • by jgardn (539054) <jgardn@alumni.washington.edu> on Thursday May 22, 2003 @09:52AM (#6014692) Homepage Journal
      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.
      • Slight correction. (Score:3, Interesting)

        by I'm a racist. (631537)

        We call this "redshift" in astronomy...

        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

  • by Blaster Jaack (536777) on Thursday May 22, 2003 @09:13AM (#6014474)
    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

    One of the first uses of this would be to make Michael Jackson even more white.
  • But when Joannopoulos and his colleagues Evan Reed and Marin Soljacic investigated what happens when shock waves pass through a device called a photonic crystal, they discovered a completely unexpected effect.

    Yay for guess and check!
    • Re:unexpected? (Score:5, Informative)

      by afidel (530433) on Thursday May 22, 2003 @09:28AM (#6014547)
      This happens quite a bit in science. The Blue LED only because practical because someone made a dopant mixture that the classical formulas said would produce a completely different wavelength. Something about the way that the spaces formed lead to a high intensity blue led that could match the output of nearly the top green and red led's, making white and fullspectrum output possible.
  • by bigattichouse (527527) on Thursday May 22, 2003 @09:13AM (#6014477) Homepage
    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.
    • by alchemist68 (550641) on Thursday May 22, 2003 @10:05AM (#6014777)
      I disagree with "Star Trek has been completed!"

      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)

    by NearlyHeadless (110901) on Thursday May 22, 2003 @09:14AM (#6014479)
    Joannopolous was also involved in the development of the "perfect" dielectric mirror, which was mentioned here [slashdot.org] before.
  • Heat - energy (Score:4, Interesting)

    by sonofagunn (659927) on Thursday May 22, 2003 @09:14AM (#6014483)
    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?
    • Re:Heat - energy (Score:5, Informative)

      by FamousLongAgo (257744) <maciej AT ceglowski DOT com> on Thursday May 22, 2003 @09:38AM (#6014603) Homepage
      Uh, what exactly is a 'heat wave'?

      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, Interesting)

      by drinkypoo (153816)
      The heat energy you are thinking of being the same as light waves but at a different frequency is near infrared radiation (or actual infrared radiation) and it is, in fact, light.

      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

  • by Anonymous Coward on Thursday May 22, 2003 @09:15AM (#6014489)
    I call it a "laser"....
  • The description in the article reminds me of the fictional workings of the Enterprise warp core.

    "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.

  • by kristoferkarlsson (621051) on Thursday May 22, 2003 @09:17AM (#6014496)
    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.
  • I can imagine (Score:2, Interesting)

    by Apreche (239272)
    An optical router. An incredible array of lenses and lasers and "light controllers". It would take up an entire room and be a dust free vacuum. It would be so awesome, not to mention cool looking.
  • DJs! (Score:5, Insightful)

    by Pharmboy (216950) on Thursday May 22, 2003 @09:17AM (#6014499) Journal
    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? :-)
  • ...all those burning posts sent my way will just give me a nice tan!
  • by EddWo (180780) <eddwo@hotpop . c om> on Thursday May 22, 2003 @09:25AM (#6014535)
    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
    • by Troed (102527) on Thursday May 22, 2003 @09:45AM (#6014648) Homepage Journal
      Uhm, it wouldn't mess up anything. A 1280*1024 colourdisplay is essentially a 3840*1024 "monochrome"-display (each R,G,B being separate elements). If you wouldn't need separate elements, you'd have a true 3840*1024 colour display, which would be vastly superiour to sub pixel rendering .. :)
    • by harrkev (623093) <kfmsdNO@SPAMharrelsonfamily.org> on Thursday May 22, 2003 @10:00AM (#6014739) Homepage
      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.

      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!

  • by stiller (451878)
    The researchers worked out that if a photonic crystal is designed in a certain way, incoming light can get trapped at the shock wave boundary, bouncing back and forth between the compressed part of the crystal and the uncompressed part, in a "hall of mirrors" effect.

    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
  • by HidingMyName (669183) on Thursday May 22, 2003 @09:28AM (#6014550)
    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.
    • even sound waves may wind up breaking the crystal

      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)

    by onthefenceman (640213) <szoepf.hotmail@com> on Thursday May 22, 2003 @09:31AM (#6014567)
    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.
    • Re:Efficiency (Score:3, Informative)

      by geeber (520231)
      The efficiency of interest in these types of processes is not the total energy efficiency. For example, if I lose heat because I have to stabalize the temperature of the crystal, I am not worried about that. What is of ultimate interest is the optical conversion effiency - the power in at wavelength one, versus the power out at desired wavelength two.

      Optical conversion efficiency is what is important, for example, in wavelength conversion for data transmission. You don't want to lose signal power.
  • by UncleBiggims (526644) on Thursday May 22, 2003 @09:33AM (#6014576)
    I'm confused. Are you saying that MIT researchers have developed a new "Cyrstal Light" drink mix that changes colors? What flavor is it?
  • by argStyopa (232550) on Thursday May 22, 2003 @09:33AM (#6014578) Journal
    I'd be curious to know the breadth of the effect (possibly limited to those wavelengths that can be captured by photonic crystals?). I mean, visible light is only a very small part of the EM spectrum. http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSp ec2.html
    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.
    • by Anonymous Coward
      It's not violating the second law of thermodynamics because to do this sort of upshift requires a stress to be applied to a crystal, thus inputting energy into the system. It's just that this energy is converted into a higher frequency light ray.
    • The 'near-100% efficiency' doesn't mean that the process is energy-free, just that the light coming out is almost as intense as the light coming in. Ordinary filters don't convert anything, they just block out what you don't want. If only 10% of the emitted light is of a frequency you want, then 90% is lost by using a filter. This process actually converts the incoming light into the outgoing, so any losses are due to imperfections in the system.
  • A pity the researchers seem determined to pander to the rednecks by doing experiments in which they fire bullets at crystals. It sounds a bit too much like those fusion machines at LL that either don't work or are now covered in secrecy (fire lasers at deuterium/tritium pellets...). That's the bit of the article I'd have left out if I wanted to be taken seriously. Terahertz imaging might be safer than X-rays, but not if the medic comes in clutching his assault rifle ("OK, we're going to shine a light on you
  • by VCAGuy (660954) on Thursday May 22, 2003 @09:36AM (#6014591)
    ...shift happens!
  • by DrFlounder (137823) on Thursday May 22, 2003 @09:37AM (#6014599) Homepage Journal

    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)

    by Domini (103836) <lailoken@gmail.com> on Thursday May 22, 2003 @09:40AM (#6014614) Journal
    Having the ultimate sunglasses... have it shift Ultra-violet to a more visible frequency...

    Or perhaps even infrared/heat?
    Cool glasses that make you see in the dark? (military applications?)

    Whee!
  • by the bluebrain (443451) on Thursday May 22, 2003 @09:41AM (#6014616)
    • 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? :)
  • This is by far one of the most pivital breakthroughs I've seen in a while. Makes me want to fire up our lasers and start playing...However, they haven't accomplished this yet..

    "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.

  • by DaLiNKz (557579)
    Does this mean my laser pointer will be able to hit the moon? :D
  • by MtViewGuy (197597) on Thursday May 22, 2003 @09:45AM (#6014645)
    Hmmm.

    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)

    by kravlor (597242) on Thursday May 22, 2003 @09:46AM (#6014653) Homepage

    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:

    • Near 100% efficiency -- I'd like to see a reproducable demonstration of this. If it is true, we will have a revolution in the solar cell industry. However, the Second Law of Thermodynamics is a difficult thing to contend with; anything that comes near 100% should set off any good physicist's red flags.
    • The article is going to be published in the Physical Review Letters -- This is significantly different than saying the article has been published in the PRL's. Such a journal is peer reviewed, which means that other respected scientists in the field have read and commented on the article and its methods, and endorse the results. This case, however, seems a lot like "cold fusion" -- with researchers calling a press conference before letting others reproduce their results.

    I hope for the best, but remain sceptical; let's hope these new shockwave effects become easier to generate and exploit!

  • by rpiquepa (644694) on Thursday May 22, 2003 @09:47AM (#6014657) Homepage
    I also commented this story here [weblogs.com], but I also previously posted another column [weblogs.com] on this subject. Please read it if you're interested by the photonic revolution.
  • by PerspectiveTransform (621772) on Thursday May 22, 2003 @09:53AM (#6014700)
    Thank god... now just before Zephran Cochran launches, we'll have the frequency shifting lasers we need to stop the Borg without any help.
  • by geeber (520231) on Thursday May 22, 2003 @09:56AM (#6014718)
    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.
  • by Arcturax (454188) on Thursday May 22, 2003 @10:45AM (#6015020)
    By taking sunlight and turning it into microwave radiation, you could get far greater efficiency out of the generation of electricity.

    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.
  • by zhamurai (229417) on Thursday May 22, 2003 @11:31AM (#6015364)
    The radiation selectivity property was discovered by observing the phenomenon of Cherenkov radiation inside the photonic crystal.

    For further more detailed technical information, a PDF of the paper is here [http://physics.ucsd.edu/~drs/publications/2003/lu o_science_2003.pdf]

    Photonic crystals fall under a broader family of materials called "metamaterials".

    Future research note: Software-programmable metamaterials will create wonderfully exotic applications.

    Cheers

    Andrew

  • by ca1v1n (135902) <.moc.cinortonaug. .ta. .koons.> on Thursday May 22, 2003 @12:26PM (#6015858)
    "Huh, that's not supposed to happen..."
  • by neirboj (567806) on Thursday May 22, 2003 @12:59PM (#6016114) Homepage

    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)

    by retro128 (318602) on Thursday May 22, 2003 @01:07PM (#6016204)
    Initially they will generate shock waves by shooting bullets at photonic crystals.

    Who says science isn't fun?
  • by istartedi (132515) on Thursday May 22, 2003 @01:49PM (#6016679) Journal

    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.

Faith may be defined briefly as an illogical belief in the occurence of the improbable. - H. L. Mencken

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