Slashdot Mirror
Intel Announces Laser Breakthrough
AdmiralWeirdbeard writes "Intel has just announced a breakthrough in laser technology allowing a continuous laser wave on a silicon chip. Apparently they devised a method to sap the interfering field of electrons previously generated in silicon by the lasers. Intel says that hardware exploiting the advance might begin appearing at the end of the decade."
The (first) article states the waveguide is 1.5x1.55micrometers and 48millimeters in length, Has it got the units right on that one?
No, those units look right. If you really read the first article, then you would have seen the picture of the die.
The (first) article states the waveguide is 1.5x1.55micrometers and 48millimeters in length, Has it got the units right on that one?
Yes. The Nature article the guys published (20 Jan, vol 433, p292) on this says "4.8 cm".
IANAEE, so maybe its correct, but their going to refine it, or maybe its not linear.
Yes, of course they're going to develop this further. This is the first time they've achived continous-wave laser gain in silicon, obviously the next step is to increase it.
(A smaller cavity requires larger gain)
No it's not linear, the cavity is S-shaped.
Yeah, they mention in the news.com article that silicon is a poor producer of light, what it is good at though is amplifying it via the Ramen effect.
A Raman laser, in some ways, is ideally suited for silicon. The Raman Effect, discovered in 1928 by Nobel laureate Chandrasekhara Venkata Raman, roughly works as follows: Light hits a substance, causing the atoms in the substance to vibrate. The collision causes some of the photons to gain or lose energy, resulting in a secondary light of a different wavelength. A Raman laser essentially involves taking this secondary light and then amplifying it (by reflecting it and pumping energy into the system) to emit a functional beam. Because of its crystalline structure, silicon atoms readily vibrate when hit with light. The Raman Effect, in fact, is 10,000 times stronger in silicon than standard glass, which should make it far easier to amplify.
~Anztac
Keep in mind that the lasers you are working with are not very precise (the CD player, DVD player), or even only have to be coherent (the laser pointer) and not pulsing. Even with the encoding, the DVD is only transmitting a few Mb/s of information as it encounters pits and lands on a CD/DVD. (4.7GB/2 hours = ~6Mb/s)
The long-haul optical systems and optical switches are transmitting over multi-kilometer fiber optic cable that is transmitting at Gb/s rates. That requires a MUCH better laser, in terms of power, coherency and switching speed. I actually don't know what the lasers cost, but some of the receivers can be in the hundreds for a single receiver at the very high end. The optical systems themselves are rather expensive, being thousands of dollars for a single mid-range board that has a pair of optical receiver/transmitters (2 ports).
Try learning physics.
Laser: Light Amplification by Stimulated Emission of Radiation.
The stimulated Raman effect is fundamentally different from stimulated emission. You can't get stimulated emission from Si because it is an indirect bandgap semiconductor. However, it is true that both processes can generate coherent beams of light, and people typically refer to devices that generate coherent light as laser sources, hence the term "Raman Laser".
However, my point is that this device can't convert non-optical energy into optical energy. Furthermore, since it's a non-linear optical process, you can only get the necessary intinsity to drive this process from a coherent source. Therefore you must have an actual laser to start this process. This is something that they state in the articles. However, in the c/net article, the marketing hype starts to take over. They state, "The Santa Clara, Calif.-based company has created a chip containing eight continuous Raman lasers by using fairly standard silicon processes rather than the somewhat expensive materials and processes required for making lasers today." Implying that this gets us away needing old-fashoned expensive lasers. It doesn't.
Yes, they are nice, small coherent light sources that can be easily modulated and integrated into Si, but they aren't lasers, and the efficiency is a problem.
Let's say you want to start making integrated optical circuits. If you want a chip with 100 switches, you must pump each switch with 300 mW. (Well maybe you could cut back to 100 mW, but the efficiency of these things is non-linear, and there will be a threshold power at which they don't work.) Therefore, a device with just 100 switches would require 10 to 30 watts of coherent optical power to drive it. Then you need to worry about the wall-plug efficiency of your pump laser (or lasers) and the bulk of the pump laser.
It's interesting, and it did deserve an article in Nature. However, there's a lot of corporate marketing hype behind all the buzz in the linked articles, and when marketing hype and science mix I get annoyed.