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Science Technology

Optical Control of Light on a Silicon Chip 129

Posted by samzenpus from the light-turns-it-on dept.
An anonymous reader writes "Researchers at Cornell University have demonstrated a device that allows one low-powered beam of light to switch another on and off, on silicon, a key component for future "photonic" microcircuits in which light replaces electrons for propagating signals. It is highly desirable to use silicon--the dominant material in the microelectronic industry--as the platform for these photonic chips. The approach developed confines the beam to be switched in a circular resonator, greatly reducing the footprint required on the chip and allowing a very small change in refractive index to shift the material from transparent to opaque."
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Optical Control of Light on a Silicon Chip More

Optical Control of Light on a Silicon Chip

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  • Shedding some light... (Score:5, Funny)

    by rooijan ( 746599 ) on Thursday October 28, 2004 @04:50AM (#10651629) Homepage
    This certainly sheds some light on the future of technology - hell, you could even say they are going to light the path of progress!

    ...sorry, couldn't help myself.

  • Comment removed (Score:5, Interesting)

    by account_deleted ( 4530225 ) on Thursday October 28, 2004 @04:51AM (#10651632)
    Comment removed based on user account deletion

    • Re:Optronic gates (Score:3, Insightful)

      by willijar ( 99554 )
      Diffraction and interferences are linear processes - you need a nonlinear process (such as the change in index used in the devices) to have one signal modify another.

    • Re:Optronic gates (Score:4, Informative)

      by Optics Geek ( 799673 ) on Thursday October 28, 2004 @12:39PM (#10655632)
      Interference is still key to this. The nonlinear optic effect here is the refractive index change of the resonator material due to the beam controlling the switch. What's different here is the circular resonator, that basically make the path in the material with the index change extremely long, so a very small index change can induce the necessary phase change for the beam to switch. The resonator sits in one path of a (waveguide) Mach-Zehnder interferometer. When the phase shift induced by the resonator path is 0, you have the "on" state. When the phase shift induced by the resonator path is pi, you have the "off" state.

  • Can somebody explain ... (Score:3, Interesting)

    by YeeHaW_Jelte ( 451855 ) on Thursday October 28, 2004 @04:54AM (#10651638) Homepage
    What is the exact use for this? Is it's advantage that there's no need to switch back & forth between electric signals & optic signals in e.g. a optical router, or is a computer based on solely optical signals faster than one based on electrical signals?

    • Re:Can somebody explain ... (Score:1, Funny)

      by Anonymous Coward
      It would be cool to have a PC that glows in the dark...

    • Re:Can somebody explain ... (Score:5, Informative)

      by DigitumDei ( 578031 ) on Thursday October 28, 2004 @05:06AM (#10651682) Homepage Journal
      correct.

      from the article itself.

      What are the applications of this device?

      These structures will find their first application in routing devices for fiber-optic communications. At present, information that travels at the speed of light through optical fibers must be converted at the end into electrical signals that are processed on conventional electronic chips. These electrical signals can in turn be converted back into optical signals for re-transmission, which in the end makes this an extremely slow process. The all-optical switch enables routing signals without the need of conversion to electronics.
      • What doesn't make sense about this is that a "router" does more than just pass packets from one interface to another. It needs to read the contents of the packets (or the headers at least), reference a routing table, decide where to send the packet, and possibly modify it. Unless there is some way to make an entire router out of optronics, RAM and all, there is really no way to avoid a conversion.

        -matthew

    • Its faster. (Score:1, Informative)

      by Tracer_Bullet82 ( 766262 )
      One: Its faster than a normal circuits.
      Two: It consume less power.

    • Re:Can somebody explain ... (Score:5, Interesting)

      by frankvl ( 817911 ) on Thursday October 28, 2004 @05:30AM (#10651747)
      Light travels about 10x faster than electrons in their optimal medium, so the potential processing speed limit is increased.

      Also, light processing does not necessarily generate heat, so there is no cooling needed to preserve the hardware, unlike the electro solution.
      • > Light travels about 10x faster than electrons in their optimal medium, so the potential processing speed limit is increased.

        What?? I thought electrons traveled at the speed of light! AFAIK the advantage of optical over electrical is that the paths of photons can cross w/o interfering with each other, thus potentially allowing for smaller processors.

        • Re:Can somebody explain ... (Score:5, Informative)

          by amorsen ( 7485 ) <benny+slashdot@amorsen.dk> on Thursday October 28, 2004 @06:03AM (#10651827)
          I thought electrons traveled at the speed of light!

          Think again. Electrons have rest mass, therefore they do not travel at the speed of light. In fact they travel really slowly in a wire, perhaps a meter per hour on a good day.

          • Hmm...aparently the answer is it depends on the medium [anl.gov]

          • Re:Can somebody explain ... (Score:5, Interesting)

            by Antique Geekmeister ( 740220 ) on Thursday October 28, 2004 @07:31AM (#10652196)
            "Think again" is right. The electrons are involved in propagating a wave of electromagnetic energy, in ways that are fun to examine. But what you are describing is the average rate of travel of an electron, much like the average rate of travel of a lake: only a little bit of water goes in and out of it, on the average, so the average speed is very slow.

            The *wave* in the lake, however, is much faster, carried by particles that bounce around each other much faster. Typical propagation speeds of electrical signals in network cable is a significant fraction of the speed of light, roughly 75% of the speed of light for 75-Ohm coax cable as one example.

            Optical propagation in fiber-optic cable, which is what this new technology will be used for, is also limited to less than the speed of light. There, you get interesting effects because it's being transmitted through glass (or plastic for short cables), but still a significant fraction of the speed of light in vacuum.
            • The electrons are involved in propagating a wave of electromagnetic energy, in ways that are fun to examine.

              Grad school cracked you too, eh?

            • Re:Can somebody explain ... (Score:5, Informative)

              by barawn ( 25691 ) on Thursday October 28, 2004 @09:12AM (#10653033) Homepage
              The *wave* in the lake, however, is much faster, carried by particles that bounce around each other much faster.

              Actually, the wave in the lake is carried by something akin to phonons (heck, they might be phonons - I hate fluid mech). That is, the wave is "transmitted" by quanta of the intermolecular forces, not by any particles in the medium itself.

              Strangely enough... as you suggested, the exact same thing happens in electrical signals, except there, the wave is "transmitted" by the inter-electron forces, which we call "electromagnetic" forces. Quanta of the electromagnetic field are, of course, photons, and the reason that electrical signals travel at 75% the speed of light is because that is the speed of light in that material, roughly.

              So, in a very real way, signals on chips have always been carried by photons. It takes power to shove electrons around, though, whereas photons will just propagate. So transmitting a signal purely by photons (rather than by photons through electrons) is lower power.
              • Lord help me, that actually made sense to me.

                All of my physics teachers would be so surprised.

              • As my former advisor used to say in a very relatex context. Yes, if you build any kind of a waveguide (e.g., stripline or coplanar waveguide, or a real one, with metal walls) and send an electric pulse down that, the resulting wave will propagate all the way to the end. And the wave can be viewed as a PHOTON (except that lower frequency than optical).

                If your metal is resistive, you'll dissipate some energy in that, the same as if your leght-transmitting medium is slightly opaque. But no, you do not need to
                • And the wave can be viewed as a PHOTON

                  Um - any electromagnetic signal can be viewed as being transmitted by photons, whether it's an electromagnetic pulse down a waveguide, light propagating through free space, or someone changing a voltage on an electrical trace, causing it to switch.

                  In the voltage-switch case, the photons are virtual. In the free-space case, they're real. But they're still photons.

                  Electron-electron interactions are caused by (virtual) photons. Electrons can't interact with each other
                  • But this one caught my eye:

                    (save in the case of a superconductor, but no one's going to suggest superconducting computers)

                    You know, it is funny but for the last 15 years of my life I've been personally involved with designing just such a beast and I can claim that I do suggest building it pretty soon... ;-) In any case, superconductor technology is way more mature than anything that photonics can offer right now.

                    Actually, the quote in GP Subj: was from my former adviser Prof. Kostya Likharev said in ex

              • Actually, the wave in the lake is carried by something akin to phonons (heck, they might be phonons - I hate fluid mech). That is, the wave is "transmitted" by quanta of the intermolecular forces, not by any particles in the medium itself.

                What an unhelpful comment. Sure, the actual force is carried between charged poles and between particles By Pho[N]ons, uh huh, at rate C, of course, bravo for your brilliance.

                The wave damn well does propagate through/via "particles in the medium itself". See that H2

              • In fluid mechanics you don't call the carriers phonons. You call them molecules. :D
                And the wave itself is called a sound wave. :)

                In a plasma there are sound waves, magnetosonic waves, and EM waves. And the carriers are either particles (atoms/molecules/electrons/ions), EM coupled movement of particles, and EM propagation with photons, respectively.

                Phonons are a phsyics term that I believe arose when semiconductor physics was first investigated. The term "phonon" can apply to pretty much anything
                • In fluid mechanics you don't call the carriers phonons. You call them molecules. :D
                  And the wave itself is called a sound wave. :)

                  I'm not talking about the carrier particles, which are electrons in a conductor, atoms in a lattice, and of course, molecules in a liquid. I'm talking about the quanta of the wave itself.

                  The wave propagates through intermolecular forces. It's quantized, just like any other propagation of energy. What those quanta are called for a liquid or a gas, I don't know.

                  And the carriers
                  • But that's not entirely correct.

                    A phonon is a quantized element (as you said). It's also the measure of vibration modes in molecules. In fluids, a phonon can exist on a per-molecule or per-atom basis. You can have phonons travelling up and down a molecule if you want; it's just a word for the vibrational modes.

                    Sound propogation in fuilds (NOT solids) is caused by kinetic interaction of molecules and atoms. Any phonons that exist are a subset of the sound wave.

                    You see the difference? Phonons re
        • Ah, there was a discussion about this in a recent thread... can't remember which though. The electrons cannot travel with the speed of light because they have mass. But they don't need travel much anyway, because the information is transmitted via the electrostatic force which can be explained as the exchange of virtual (light-speed fast) photons. So the first electron in the wire gets pushed a bit and in turn pushes the second electron in the wire and so forth, much like when you push one end of a stick an

          • Re:Can somebody explain ... (Score:2, Informative)

            by Anonymous Coward
            I like your explanation why information is transported with approximately speed of light in conductors, but the reason why electrons travel much slower is different:

            The reason why electrons travel at a finite (rather slow) speed is scattering with the crystal lattice. If you apply a voltage, i.e. create an electric field along a metallic wire you would in principle continously accelerate the electron along the wire to an kinetic energy that corresponds to the applied voltage (e.g. 1eV for 1V of applied vol

      • Re:Can somebody explain ... (Score:5, Informative)

        by TheRaven64 ( 641858 ) on Thursday October 28, 2004 @06:27AM (#10651894) Journal
        Light travels about 10x faster than electrons in their optimal medium, so the potential processing speed limit is increased.

        Umm, the speed of electron travel is irrelevant. I assume you've seen a Newton's cradle (a set of 4 or more balls on string arranged in a row. You swing the end one or two and when it hits the stationary ones the corresponding ones at the far end swing). The balls in this are only moving at a few meters per second, while the signal (when the balls collide) is moving at the speed of sound. In a chip, the individual electrons move relatively slowly, but the signal moves at the speed of light.

        The problem with using electrons is that two electrons can collide. This means that your circuit paths can not cross. With something the complexity of an IC, this means that a lot of space is wasted just routing electrical paths around each other. The analogy I was given when I saw something like this demonstrated a few years back was that designing an electronic chip was like trying to lay out the road system in Great Britain without any roads crossing. Photons, on the other hand, can pass right through each other without interfering (quantum mechanics is magic like that). This means that signal distance between any two components on a chip is the same as the straight line distance (on an electronic chip it can be significantly further). This is good news, because we are starting to get close to the light speed limit with current ICs. A 3GHz chip must pass data from one pipeline stage to the next 3,000,000,000 times every second. Light can travel (roughly) 10 cm in this time. Scale this up by a few orders of magnitude and you start to get some real problems with component density.

        • Correct.
          What this means for us in the short term future, is that switching to completely photon ICs will allow us to use larger in size microchip dies than current dies without reducing the clock speed. Obviously in the longer term this means much much smaller dies sizes and at least 1000 times faster clock speeds.

      • Additionally, an optical circuit has the advantage that two beams of light can cross each other without interfering harmfully with each other. Obviously you couldn't do this with in an electric circuit. This allows optical circuit designers to make more compact designs, and it's a lot easier to do. With circuits on microchips today being so complicated, you need some pretty hefty programs to actually to the designing. The same optical circuit could be much smaller and eaiser to design.
        • Yes some guys managed to use 40 beams for an intercontinental Internet connection; each user got 10 Gbit/s up&down access, rather than 10Gbit/s shared.

          It will be even more interesting when it can be applied to circuitry! You were damn right mr. Moore..

    • Re:Can somebody explain ... (Score:5, Informative)

      by Anonymous Coward on Thursday October 28, 2004 @05:41AM (#10651778)
      This isn't for optical network switches, this is for processor cores.

      IAAEE, so here goes a simple explanation of why optical is more desirable for a processor.

      1: Faster signal propagation. In the GHz region propagation delay can cause major timing headaches in synchronous computers (one reason your system bus is always slower than your CPU: the physical length of the clock lines on the motherboard introduce too much delay to properly synchronize at really high speeds).

      2: Higher slew rates. Another limit on clock speed is the rate that the logic gates can change state, which is proportional to the power consumption (it takes more power to change the state of a logic gate more quickly). Theoretically, an optical switch uses the same amount of power regardless of speed because youre switching an optical state rather than energizing (or de-energizing) a circuit.

      3: Lower power consumption. Because you aren't using ever-higher currents to force electrical states at higher speeds, your driver circuitry doesn't need to be as robust. This also leads to:

      4: Lower cost. Less circuitry to push around large signals means you can save die area on the chip.
      • This isn't for optical network switches, this is for processor cores.

        Last time I checked, network switches had processors in them. No doubt this technology will make it into consumer PCs in the future, but for now it's more likely to make it into specialized applications like network switching.
        • I believe when he said "optical network switches" he meant the physical part of the switch itself that deals with the optical data coming in and out. Obviously what we call a "switch" has a processor in it, but he meant the more rudimentary "on-off" type switch. The conversation above was about that.

          -Jesse
      • Of course it's for "optical" switching!
        Well, for the optical modules in a switch, anyway.

        There's a much more obvious application for this than optical CPUs.
        It's every optical networking component maker's wet dream to be able to modulate light on silicon, as this would bring down costs of optical modules for 10 Gb/s, 2.5Gb/s, etc. In principle, you could live without the expensive optical components (pin-diodes, EAMs) and do it all this on one single piece of silicon.

        Now we just need to find a cle
    • "What is the exact use for this?"

      How many pins are on the latest AMD64? 939? 940? something like that. Optical interconnect could reduce that to single digits.

      I'm not sure what loading concerns there are with optics... one problem I run into in my designs is needing to connect to many other devices, and that slows things down.
  • Comment removed based on user account deletion

    • Re:Light switching CPU mentioned before? (Score:4, Interesting)

      by amalcon ( 472105 ) on Thursday October 28, 2004 @05:18AM (#10651710)
      (must need a huge heatsink).

      Actually, one of the major benefits of optical computing is that you don't need a heatsink at all. This is because the heat put out by a CPU is due to inefficiency (in other words, because they are not room-temperature superconductors). There is little to no inefficiency in modern optical cable, especially compared to copper wiring.
      • There is very little loss in the FETs in a CPU either, until you start switching them really fast.

        I'm pretty sure there will be switching losses in optical switches as well, especially while they are changing state. Optical CPUs probably won't need a heatsink until they become very advanced and operate way above the speeds achievable now, but its likely they will eventually. After all, the first few computers I had didn't need a heatsink either.

        -Daniel

      • Re:Light switching CPU mentioned before? (Score:5, Informative)

        by jannic ( 152373 ) * on Thursday October 28, 2004 @05:53AM (#10651804)
        This is not true, at least for this kind of optical switch. In the article, the authors state that it takes 0.15pJ to generate the free carriers. This sets a single switch to 'on', a single time, for about 500ps. If you assume that a switch is turned on, on average, 50% of the time, a single switch would consume 0.15mW. An optical CPU with one million switches would therefore need 150W, at 2 GHz. If you want a faster switch, you must reduce the carrier lifetime. Therefore you need more pump power to keep the switch turned on. So power consumption would increase linearly with clock speed.
        And these numbers do not include any other losses, and assume that you can recover all the pump light which is not absorbed in the ring. If you don't recover that pump light, power consumption goes up by a factor of 166. (So you'd need 25kW for the 2GHz CPU with 10^6 switches...)
        • IANAEE, but if the system is very efficient, it doesn't matter how much power it's consuming with regards to the consumption of the CPU. An optical CPU should still generate far less heat than an electronic CPU with far lower efficiency, given the same levels of power consumption.

          I'm probably wrong, because again I'm not an electrical engineer...
      • There is loss in an optical chip as described here. When gates are set to "opaque" mode, light that hits them is either absorbed or reflected, and if reflected, eventually absorbed somewhere else. Light that passes all the gates is eventually absorbe by a detector or by the switch portion of another optical gate. (remember that ALL energy put into a processor eventually is turned into heat, it doesn't just disappear)

        All of the absorption translates the energy of the light to energy of heat. Don't fool y
    • I believe that one of the reasons optical CPUs are attractive is that they WOULDNT need a huge heatsink. The heat in chips is caused by the losses when the transistors switch, optical CPUs don't have any transistors so don't have these losses. There will probably be a loss of light which could heat up the chip in a similar way, but I can't see why speed would have anything to do with it in an optical CPU. Speed effects the heat in electrical CPUs because higher speed = more switching = more switching losse
    • Well, it certainly wouldn't have been an optical cpu you are thinking about.
    • That was actually a DSP. And it was a DSP built for a specific purpose. It was a military application/experiment if I recall correctly.

  • Great commercial slogan potential! (Score:3, Funny)

    by GozzoMan ( 808286 ) on Thursday October 28, 2004 @05:10AM (#10651696)
    "FASTER THAN LIGHT COMPUTING!" ... uh, "fast-AS-light" in fact. damn, never mind.
  • Any idea exactly how fast this would be? Its power requirements? How long until people start seeing this used in "real" situations?
    • The 'switch', as presented in the article, is far from useable in real applications, especially for fast optical computing. If you look at Fig. 3, you see that it switches on very quickly (a few ps), but switching off, again, is relatively slow. It takes on the order of 500ps, so switching speed is limited to ~2GHz. (Probably lower, because after 500ps, only half of the free carriers recombined)

      But they also noticed that faster carrier recombination could be reached by surface modifications, or ion implant
    • Your guess is as good as anyone else's. There's enough that we don't know about this stuff to make any somewhat exact answer meaningless.

  • Why silicon? (Score:2, Interesting)

    by ChrisMDP ( 24123 )
    It is highly desirable to use silicon...

    What the poster and the article both neglect to mention for us simpler types is why silicon is desirable.

    Is it simply because it requires less modification to the production pipeline, or is there another more scientific reason?

    Perhaps a scientific slashdotter can enlighten us. Ahem.

    • Re:Why silicon? (Score:3, Interesting)

      by amalcon ( 472105 )
      IANA...well, I am not a person whose speculation on this matter should be taken seriously. Nonetheless, I would wager that the reason for this is: Silicon is very common on Earth. As I recall, it's the most common element which is solid at room temperature. This makes it inexpensive.

    • Re:Why silicon? (Score:5, Informative)

      by flyingman ( 230455 ) on Thursday October 28, 2004 @05:41AM (#10651777)
      Because silicon is well established in the semiconductor industry and therefore cheap to obtain easy to process into semiconductor devices.

      On the other, almost all optical devices (LEDs, laser diodes) are made from III-V compund semiconductors like Galliumarsenide (GaAs), InAs, AlAs, GaN, GaP and so on. These are not available as large crystalline blocks and thus there are no such things as 300mm wafers. They are usually fabricated by expensive methodes. However, they are the only practical solution because the are so-called direct semiconductors - you just cannot do optics with indirect band-gap semiconductors like silicon.

      Now, if you find THE technological trick to do optics with silicon, you benefit from the cheap silicon technology and are ready to build optical computers with cheap fabrication technology. There are some tricks around already like mixing silicon with germanium (SiGe) or putting in nano-crystals so the silicon are catching up in doing optics.

      • Re:Why silicon? (Score:5, Informative)

        by hopey ( 172229 ) on Thursday October 28, 2004 @06:25AM (#10651888)
        My research area is silicon based optoelectronics and we are trying to fabricate efficient light emitting silicon based components. Basic components are made from MOS-structures with incorporated excess silicon to the silicon dioxide layer. After this the device is annealed at high temperature and the excess silicon forms so called nanocrystals inside the oxide. This allows the direct electron transition like in III-V group semiconductors.

        In basic structures the efficiency is however very poor. All kinds of tricks are needed in order to get the efficiency in range of direct bandgap semiconductors. We do not know yet if it is possible :)

        One of the reasons to use silicon for IC technology is its very good native oxide. You can produce dielectric with breakdown voltages of 10MV/cm with only annealing in oxygen. Think about it 100 nm of silicon dioxides breakdown voltage is over 100 V!
    • Because all or most of the fabs are geared towards Si CMOS circuitry, and without a clear path for these multi-billion production facilities to migrate to, the big players in the semiconductor electronics industry are not going to budge one inch from their "roadmap" (google for it - don't have time). Hint: GaAs or other more exotic direct bandgap semiconductors are not on their "favoured" list.
    • It's cheap, it's easy to machine into micro-structures like teeny-tiny little transistors and electrical components, and eventually you have to connect it to something else. If it's silicon the whole way from optical switch to controller switch to CPU to whatever, everything can be much smaller and integrated into the same component without extra places to connect devices to each other or have extra leads. Think the difference between transistors, millions of them on a chip for your CPU, and having to do i
    • Si is a good waveguiding material and its optical properties are well known. That is the bottom line.

      If you make everything on a silicon chip, you can create complex devices the require no chip-level post wafer integration. That is currently the case for electronics based chips, like your CPU. Compound optical devices at present cannot be integrated in the same way. This thing is effectively a transistor switch done opticaly (and most importantly at low power compared to the transmitted signal power[actu

  • How good? (Score:3, Interesting)

    by F'Nok ( 226987 ) on Thursday October 28, 2004 @05:12AM (#10651705)
    These structures will find their first application in routing devices for fiber-optic communications.
    That's a fantastic use...

    But I'm more interested in optical computing.

    In theory extrememly low power chips should be possible, but what is the absorption rate like, especially in terms of heat, and quantity of reused light.

    That is ofcourse, assuming that this CAN be used for more sophistication chip design.

    Has there been any suggestion of other uses, and if so, what possibilities are there available for such technology?

  • Many Hands... (Score:3, Funny)

    by zenmojodaddy ( 754377 ) on Thursday October 28, 2004 @05:20AM (#10651718)
    ... make light work.
    • Quite right, it wasn't really Tom Edison that invented the light bulb, it was his assistant, a native american, Many Hands.
      • Quite right, it wasn't really Tom Edison that invented the light bulb, it was his assistant, a native american, Many Hands.

        Not only that, but it only required 1/3 of him to screw in a light bulb.

  • It took a team of 17 people, bravo all... (Score:4, Funny)

    by joelethan ( 782993 ) on Thursday October 28, 2004 @05:37AM (#10651764) Journal
    Because as we all know:

    "Many hands make light work!"

    The Cornell Nanophotonics Team [cornell.edu]

    /JE

  • ahhh.. (Score:1, Funny)

    by mr_snarf ( 807002 )
    The approach developed confines the beam to be switched in a circular resonator, greatly reducing the footprint required on the chip and allowing a very small change in refractive index to shift the material from transparent to opaque
    Ahh, they finally saw the light.
  • could this directly exploit optical fiber carried data ?
    at this moment, we still need some converter in between, otherwise, we'd make it even faster than now.

    Anyway, it might open us to new perspective... optical logics would be one, where we'd have "red", "green" and "blue" components which would be combined in some ternary/quaternary way (don't know which, yet).

    Finally, this "color approach" also reminds me of some subparticle-related theory where color are also suggested...
    • You're thinking of Quantum Chromodynamics, the theory that describes the interaction of quarks, gluons and nucleons at the nuclear/sub-nuclear level.

      Though quarks are described as having 'colours' (red, blue green) these are not colours per se but are more in the vein of electric charge, although there are three states rather than two (+/-).

      And here's the obligatory link to assure readers I didn't pull this out of my arse. (I did, but they don't need to know that.) IANAP but I have a casual interest in the

  • Finally, a use for all those colorful tubes of light.
    • Actually, I imagine that this technology will turn the casemod industry on its ear. You certainly wouldn't want your cold cathode lamp interfering with your CPU operation. No strobe lights in your case. The CPU die will be using photons rather than electrons, so no doubt the CPU will be MUCH cooler, and there will be no need for watercooling or peltiers. Windows on the side of cases may disappear, because you wouldn't want someone to use flash photography and make your PC lock up.

      This pretty much sums up m

  • Christmas lights? (Score:3, Funny)

    by Danathar ( 267989 ) on Thursday October 28, 2004 @06:26AM (#10651892) Journal
    Ooooo.....This should make my Christmas tree which uses fiber optics MUCH more interesting!

  • Switching time?? (Score:2, Interesting)

    by TooTechy ( 191509 )
    What's the darn switching time? Can't find it. The really important measurement and I can't find it.

    Herriot-Watt were doing this on a physically bigger scale back in the 80s and managed something like a 10ms switch speed.

    • Re:Switching time?? (Score:4, Informative)

      by pkhuong ( 686673 ) on Thursday October 28, 2004 @07:03AM (#10652034) Homepage
      From TFA:

      To turn the switch "off," a second beam of light with a wavelength in the same spectral range is sent through the system. This wavelength is absorbed by the silicon through a process known as two-photon absorption creating many free electrons and "holes" (positively charged regions) in the material. This changes the refractive index of the silicon and consequently shifts the resonant frequency of the ring enough that it will no longer resonate with the 1555.5 nanometer signal. The process can theoretically take place in a few tens of picoseconds.

      Very interesting stuff... It's kind of like EIT, but much more sensitive.

  • My God (Score:1, Funny)

    by Anonymous Coward
    Imagine a beo... never mind

    • Re:My God (Score:3, Funny)

      by TeknoHog ( 164938 )
      "My God, it's full of stars!"
      "Nope, that's just a Beowulf cluster of optical Linux boxen. Nothing to worry about."

  • A Fair comparison (Score:2, Interesting)

    by slackerny ( 824897 )
    I do not see any use for optics in processing even though photons theoritically travel faster than light. (Remember photons also do not travel at 3*10^8 in a waveguide eg silicon: velocity = c/refractive index and refractive index of silicon ~= 3.5)

    although this would boost the oppurtunity for optics in processing... I do not believe it would be usefull in high speed processing simply because it would be drain lot of power (wall-plug efficiency is being worked on to improve right now!) but this could chang
    • here is a fair comparison of wavelengths.
      -optical wavelength = 1.1 microns. electronic wavelength
      -(electrons can be compared in energy to an x-ray photons and so wavelength of x-ray photon - this concept is used in electron microscopy) this is in nanometers 2 orders smaller.

      OK... first off I don't know anything about this. That said, by optical wavelength, I'm guessing 1.1 microns is a particular color of the visible light spectrum. My guess would be that this technology could work with more than just one
      • Also, someone was talking about photons being able to cross paths without interference. However... Thomas Young's famous double-slit experiment seems to prove otherwise, but like I said I'm not an expert and so would welcome someone's more educated input.

        To get interference, you must have two light beams in the same location. The double-slit experiment works because you have two light beams both striking the target at the same spot.

        However, this is a completely different situation. Crossing two light b
      • 1.1 micron is in the infra red region (Optical is a misnomer) of the electromagnetic spectrum... It is called optical only because of historical reasons.

  • Nanovation (Score:1)

    by Anonymous Coward
    Research on ring resonators has been ongoing for many years and this research at Cornell is great.

    In the boom a few years ago, Nanovations Technologies was a start-up that touted ring resonator technology (in InP not Si). They blew their wad on big trade show booths and bus ads. Nanovation also gave MIT a piece of paper that said they wil give $90Million for research over a period of six years: I don't think MIT got much cash.

    Research for this company came out of Northwestern University. Manufacturing
  • I remember back in 1990, AT&T had a 4 bit optical computer on a lab bench. I believe it coded data in PCM laser patterns, which were stored in extremely long fiber spools (thousands of Km). Is there any descendant of that technology extant, where lasers are stored by traveling through extremely long distances in a medium?

  • Interesting, utility in question (Score:1, Interesting)

    by Anonymous Coward
    Nonlinear switching and wavelength conversion in
    small rings has been shown before, perhaps not in
    silicon. The use of absorption here is going to
    give you a significant switching recovery time and switching energy (power consumption and heat dissipation). You will also probably find that the repetition rate was quite low, because the absorption-induced heating of the ring will also shift the resonance and cause a long-time-constant shift that can be troublesome. At a minimum this will induce bit pattern de
  • Set the quantum spin states of photons leaving a laser, entangle pairs of them, and batch process them in these transphotors. 21st Century LAN parties happen frames per femtosecond and bits per picosecond.

  • The only device that anybody should ever need to control light is "The CLAPPER".


    You guys and your bloody semiconductor devices...
  • What is the equivalent (silicon transistor) gate size for a photonic switch? (E.g., 13nm for recent silicon fab processes.)

    How fast does it switch? (E.g., 2.4GHz for currently affordable Pentiums.)

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