Faster lasers for telecommunications

Researchers at Stanford University have developed a new laser technology which wastes less energy than today's lasers and is faster, able to operate at rates exceeding 100 billion bps.

Current solid-state laser technologies have become vital components in telecommunications and networking equipment, but are reaching limits in speed and efficiency. But now, researchers at Stanford University have developed a new laser technology which wastes less energy than today's lasers and is faster, able to operate at rates exceeding 100 billion bps. And because up to 400,000 lasers will be able to fit within a square centimeter chip, this also means that this new technology will be cheaper to manufacture. So far, this technology is only working in labs, so it might take some time before the industry adopts it.

This new laser technology has been developed by electrical engineering Assistant Professor Jelena Vuckovic and doctoral student Hatice Altug, who is part of Vuckovic's group at the Nanoscale and Quantum Photonics Lab.

Below is a picture of Jelena Vuckovic in her lab (Credit: Stanford University). Here is a link to a larger version of this photo (3,008 x 2,000 pixels, 1.95 MB).

Jelena Vuckovic in her lab

How does this new laser technology work?

The new laser is based on a photonic crystal, a square layer cake of indium phosphide-based material that is 300 billionths-of-a-meter (nanometers) thick and that is etched to create an array of regularly spaced, 400-nanometer-wide holes through the cake. At regular intervals among the holes are areas where no hole has been etched, called microcavities, which trap light. The filling of the layer cake is four layers of indium gallium arsenide phosphide. Each layer is called a "quantum well."
How does the laser work? When Vuckovic shines pulses of light onto the crystal, the energy that the light "pumps" into the quantum wells excites them to emit light of a desired wavelength. That light then bounces around in the microcavities and back into the wells again, setting off a chain reaction of light emission from the crystal that produces a laser beam.

And here are some details on how this new laser technology promises to be more efficient than current ones.

Researchers recently have made lasers using just a single photonic crystal microcavity in an attempt to outdo vertical cavity surface emitting lasers (VCSELs) [, which are way too weak.]
Vuckovic and Altug's laser successfully combines 81 microcavities (in a 9 by 9 array) to make it more powerful, and it operates with greater energy efficiency. In fact, [in Vuckovic and Altug experiments,] their laser was about 20 times as efficient as single-cavity lasers, putting out 100 times more power (12 millionths of a watt when pumped with 2.4 thousandths of a watt).

This research work has ben published by Optics Express under the title "Photonic crystal nanocavity array laser" (Vol. 13, No. 22, Pages 8819-8828, October 31, 2005). Here are two links to the abstract and to the full paper (PDF format, 10 pages, 1.19 MB).

Sources: Stanford University news release, November 7, 2005; and various web sites

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