Lasers blink through silicon chips

Engineers at the University of Texas at Austin have designed a chip made of silicon 'photonic crystals.' This chip acts as a silicon modulator which controls the transmission of laser light while using 10 times less energy than current silicon modulators. This could lead to optical interconnects for computers and other devices.

Researchers have tried for years to use light to carry data because it's much faster and efficient than current interconnections used in telecommunications and computers. Now, engineers at the University of Texas at Austin have designed a chip made of silicon 'photonic crystals'. This chip acts as a silicon modulator which controls the transmission of laser light while using 10 times less energy than current silicon modulators. The researchers are now working to combine these chips with lasers on a silicon platform to develop commercially viable optical interconnects for high performance computers and other devices.

Here are some short quotes from this news release.

Ray Chen, a professor of electrical engineering, and graduate students Wei Jiang, YongQiang Jiang and Lanlan Gu [from his research group,] created a chip made of silicon "photonic crystals" whose complex internal structure slowed light traveling through the chip. The laser light slowed down enough that a small electric current could alter, or modulate, the pattern of light transmission.

Below is a picture of the experimental installation, which shows "a close-up of the two voltage probes (angled wires) contacting the surface of the green silicon chip with the photonic crystals where laser light's transmission is slowed in order to modulate it" (Photo credit: Jennie Trower, for UT Austin). Here are two links to a larger version (2.21 MB) and other images.

Laser light transmission through silicon chip

These findings about this silicon modulator have been published by Applied Physics Letters under the name "80-micron interaction length silicon photonic crystal waveguide modulator" (Volume 87, Issue 22, Article 221105, November 28, 2005).

Here are two links to the abstract and to the full paper (PDF format, 3 pages, 300 KB). And here is how the UT Austin news release summarizes this research paper.

That article described how less than 3 milliwatts of power was needed for light modulation. The length of the special silicon chip the light needed to travel before being modifiable was 80 micrometers (.08 millimeters). That is about 10 times shorter than the best conventional silicon optical modulators. Smaller components help drive manufacturing costs down,and also transmit signals faster.

And here is what the researchers did to slow the light.

The shortened length was possible because Chen’s laboratory designed the silicon photonic crystals that are the key component of the modulator to have large regions of regularly spaced, nanosize holes that light would have to traverse. Navigating the Swiss cheese-like regions of the crystals, called line defects, slowed the light’s passage considerably.

With such results, the researchers are reasonably optimistic about the future. And they think that their "optical chips could become a mainstay of consumer electronic devices, telecommunication systems, biosensors and other devices."

Sources: University of Texas at Austin news release, January 17, 2006; and various web sites

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