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."

Comments

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.