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Engineers Report Breakthrough in Laser Beam Tech
petralynn writes to tell us the New York Times is reporting that Stanford engineers have discovered a method to modulate a beam of laser light up to 100 billion times a second. The new technology apparently uses materials that are already in wide use throughout the semiconductor industry. From the article: "The vision here is that, with the much stronger physics, we can imagine large numbers - hundreds or even thousands - of optical connections off of chips," said David A.B. Miller, director of the Solid State and Photonics Laboratory at Stanford University. "Those large numbers could get rid of the bottlenecks of wiring, bottlenecks that are quite evident today and are one of the reasons the clock speeds on your desktop computer have not really been going up much in recent years."
The NYT story is pretty light on the technical details....a more detail-oriented write-up can be found here... and you don't have to register to read it.
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Is that the one across the bay from Berkly?
"I'd rather be a lightning rod than a seismometer." -Ken Kesey
But will it pop a huge jiffy-pop container in my professor's house by shooting it from a plane?
...was chips with frickin' laser beams!
That's awesome. I can't wait for Hraverd and Yalle to catch up.
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This sounds silly to me since desktop power (say a $500 system - discounting monitor and keyboard) is increasing exponentially, doubling every two years compared to the price. The machine I built this spring was twice as powerful than a system I built in 2003 for the same money, but 8 times as powerful as a machine I built just 6 years ago and is about 128 times as powerful as the machine I had when I went to college in 92. And I am only considering pure clock speed, not increases in the efficiency of chips, growth of RAM and disk for the price, etc. While Moore's law concerning silicon chips will start faltering as we approach 2020, I have been nothing but impressed with how desktop performance continues to improve.
These new laser improvements, and things like molecular computing, will help us continue on after the 2020 mark with our current exponential growth.
Sorry to go off, I just got done reading The Sigularity Is Near
Great ideas often receive violent opposition from mediocre minds. - Albert Einstein
The speed of the electrons is on the order of cm/s, and is related to the current density.
.. . . .
The electromotive force, or voltage, travels at about the speed of light.
Picture a hose of water. The water (electrons) takes a long time to get from one end to the other... but the effect of putting water in one end is immediately seen at the other end (within reason).
With AC, electrons never really gain ground in a balanced load situation. Back and forth and
The modulation. The signal travels at about the same time, but you can turn it on and off much much faster... so the density of bits per unit of time is much higher.
Normal signal: ____----____----____----
0 1 0 1 0 1
New hawtness: _-_-_-_-_-_-_-_-_-_-_-_-
010101010101010101010101
Both took the same amount of time to travel down the pipe. But one conveyed 4x the information.
"Trolls they were, but filled with the evil will of their master: a fell race..." -- J.R.R. Tolkien on Olog-hai
The Silicon Solution
It describes what I believe is the same breakthrough in considerable detail. The Big Deal is that lasers can now be made from standard CMOS silicon fab processes, meaning you can integrate the lasers and optoelectronics directly into the chip without needing radically new chip fab techniques. Really interesting stuff!
If you don't know where you are going, you will wind up somewhere else.
It would also be interesting to know how much heat is generated by the absorbtion of the light. How does this compare to electrical units' heat?
The speed of electricity in a wire is not really the issue (it's about half the speed of light, I think. I'm sure someone will correct me). The real issue is signal propagation. When a transistor switches from closed to open or back, the electrical signal travelling through the wire is not a perfect on/off. The voltage ramps up or ramps down as some function of the length of the connection, width of the wire, conductivity, leakage from the transistor, inductance, ... The system needs a bit of time to "settle" into the new high or low state. This is a big limiting factor in the clocking of modern CPUs. For communication off the chip, it's far worse. Now the lines are no longer 90nm (or whatever the chip was made at) in width, and have to go through a far longer distance. That's why today's processors are limited at around 1GHz to the outside world, while internally they can be faster.
Optical interconnects alleviate many of these problems. With a laser, the ramp up time is significantly shorter, there's no capacitance in the system, and it is far less prone to interference. So, on a 100 GHz optical link you can multiplex 100 1GHz pins (essentially running a P4's FSB on two wires instead of something like 180), thereby significantly reducing the pin count. Or you could run the pins 100 times as fast, meaning much less processor waiting on RAM or bus data.
Yeah, that's not true. I don't know how fast an electron moves (I'm assuming not the speed of light, since they have mass, and that quantum physics I know little about probably comes into play), but in a normal conductor they don't move very far before slamming into something. Individual electrons don't move that far or fast on their own, it's the aggregate and resulting field that really moves.
But that's not really the problem. Transmit time is still quite low (I've heard 1ns per 6 in of trace on a board). Latency isn't really the problem. The problem is -- how fast can you change the signal? That's bandwidth. Here electrical conductors suffer because of parasitic capacitance and inductance, skin effects, reflections, induced current from nearby conductors, and a whole host of other signal integrity issues. It gets worse the longer the channel is and the more things you have connected to it. If you're wondering why the MP Pentium 4s have been on a 100MHz QDR front side bus since they were released, this is why. It's also why even point-to-point interconnect like AMDs has only recently broken 1 GHz.
Optics don't really have this issue. Two fiber optic cables next to each other don't interfere with each other. You don't have to overcome the capacitance of the channel to change from one value to the next. You just send photons of one frequency, and then switch to the next. As fast as you can switch is how much bandwidth you can get.
Alright, I'm not really liking this explanation anymore. To just directly answer your question: the advantage is 100 GHz interconnect in a way that could potentially be built into chips.
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Quantum computers are great, in theory, but even if we are able to figure out how to build one that actually works they are only capable of solving certain types of problems. Our present understanding of quantum physics tells us that you can't design a quantum computer that can do all the same math problems as a generic Intel/AMD CPU (e.i. run Windows; play Counterstrike; etc.).
That being said, the problems that can be solved by quantum computers tend to be the ones that would take a regular CPU until the end of the universe to perform (break strong encryption, large traveling salesman problems, etc.). At some point, if we can make a quantum computer compact enough, we might end up having quantum co-processors built into out PCs but we'll probably never see the CPU of our PC replaced by a quantum computer.
The tech being discussed in the article would be directly applicable to making generic PCs run faster (though it could also have the potential to improve communication speeds with a hypothetical quantum computer as well). Another tech that will probably be leveraged to make generic systems faster is the replacement of silicon in computer chips with diamond. Since diamond can handle vastly higher temperatures than silicon, without melting, it is theoretically possible to push the clock speed on a diamond based CPU much higher than on today's silicon CPUs.
-GameMaster
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#1 - The DM is always right.
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What these guys have found is a physical effect that possibly could lead to fast modulation of light. Neglected in the press release are a few fairly important issues:
All that being said, this is still very exciting. It is a new physical effect demonstrated in a silicon-based material, and a physical effect that has been used elsewhere to do useful things. Hopefully a real modulation device will come along shortly.