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."

Desktop power not going up much?

[Omega1045]

and are one of the reasons the clock speeds on your desktop computer have not really been going up much in recent years

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 [amazon.com]

What wavelength?

[Orthogonal Jones]

If I remember correctly, QCSE uses excitons to absorb light.

What is the wavelength of these excitons in SiGe? If it's significantly different than 1.3 microns - 1.5 microns, then this is a short-haul play -- like inside a box. In any case, 100 Gb/s is generally fragile stuff anyway over long distance, so it's highly unlikely that this is part of some global supercomputer, as the article suggests.

That's OK, though. This might be great stuff for optical interconnection buses.

BTW, D.A.B Miller is a big name in the field, so this is likely a big deal.

Re:Obligatory Reference

[sameerdesai]

Actually they were dolphins (Google cache) [72.14.203.104]

Re:Digital Bandwidth?

[amliebsch]

You might want to check out this article that appeared in IEEE Spectrum magazine:

The Silicon Solution [ieee.org]

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!

Heat dissipation?

[andyo]

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?

Opportunity for new "PCB" makers

[G4from128k]

This tech will mean a new opportunity for a new kind of "PCB" maker. Circuit boards with embedded optical traces will replace (or layered on to) traditional electronic circuit boards. New optical chip-to-board interconnects will also become a new, growing business. I know that people do make all-optical circuits (I've seen these at Lucent's museum in NJ), but it looks like the current tech is very expensive (etched channels in a sliced wafer).

The first company to develop a low-cost, high-quality tech for "printing" optical traces will make a mint once these interconnects become common. I'd bet that the ultimate technology will be a sandwich of resins with etched channels and vapor-deposited reflective layers, walls, corners (or high-index resin filling). For most applications, the optical interconnect can be single-layer because the non-interference on crossing beams will let two traces/channels cross each other with interference.

Inventions like this one are a great start. But until they find away to make cheap circuits to route optical connections on a board, this tech won't see widespread adoption.

Re:More informative article:

[amliebsch]

Or, if you really want technical, skip the write-up altogether and read what some of the Intel engineers had to say.

The Silicon Solution [ieee.org]

Re:Desktop power not going up much?

[Omega1045]

I am not referring only to pure clock cycles. I actually think the trend towards multi-core is a good thing. First, in modern computer enviros where multiple threads are running, multi-core systems should prove to be very effective. Second, multi-core systems will use less power than a single core system with the same total processing power. This is simple EE - multi-core means power consumption goes up in a linear style instead of as a square function. It does not matter how it is technically getting done, system are still increasing in FLOPS at the rate I mentioned. I applaud faster machines via this new laser tech, but my point still stands. Computers are still increasing in processing power in the exponential terms I mentioned. I just compared the system I built earlier this year (in Feb), and I can almost get a chip 50% faster for the same price now.

Overstated results

[PhysicsPhil]

Somewhere between the lab and the press release things got overstated. Since my PhD is in silicon-based optoelectronics, I am familiar with this kind of work. A few thoughts crossed my mind after reading the paper.

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:

• They haven't demonstrated any time-resolved optical effect, and are inferring it strictly from what might be possible. I have no doubt they can modulate, but the operational speeds are still guesstimates.
• The effect that was demonstrated is not within the 1550 nm wavelength window used for telecom traffic. Their current work shows the effect right in the middle of an H2O absorption peak. Can the effect be shifted? Probably, but these sorts of things are always more work than expected.
• From a practical standpoint, other Quantum Confined Stark Effect devices often show a strong sensitivity to the polarization of the input light. Ensuring a known input polarization is a major problem right now in optoelectronics. Lord knows it was (still is, actually) a major hassle in my research
• This device is not quite as CMOS compatible as might be hoped. Building strained germanium quantum wells on a silicon substrate requires depositing atoms layer by layer, and is a slow process. Process throughput will no doubt be an issue.

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.