U of T tests out method to ‘paint’ lasers onto microchips

Canadian researchers are proposing a solution to a potential long-term problem in microprocessor design that will “paint” lasers onto components.

The University of Toronto‘s Electrical and Computing Engineering Department published a paper Monday in Optics Express which describes how nanocrystals dissolved in chloroform or other solvents like paint could be “drop-cast” on any surface while keeping their optical properties. This means they could be used to create a laser that carries data through an optical wave, rather than the copper wire that is commonly used in silicon chips today.

Microprocessor experts are looking at ways to maintain and increase chip speeds while recognizing that they are reaching a capacity limit, or interconnect bottleneck. Light would be a faster way of handling computations than wires, but silicon does not emit light efficiently. Nanocrystal-based lasers could be used to transmit, handle and manipulate electrical signals on a chip instead of silicon, said Sjoerd Hoogland, a U of T post-doctoral fellow and the first author of the paper.

“There is no way there will be a silicon laser coming out that will answer all the demands of these optical interconnects,” he said. “We’re using well-established etching processes to create certain shapes and resonators into a silicon chip and either spin-cast or drop-cast on top of them.”

Once dissolved in a solvent, for example, the nanocrystals could be smeared or painted onto a glass or silicon slide. The laser beams created from these nanocrystals would be visible in infra-red light and could then be used to transfer data from one optical wave to another on a microchip or a circuit board. This could create major increases in speed by hundreds of gigabits per second, Hoogland added.

Although the microprocessor industry is expected to run up against the interconnect bottleneck in less than five years, Hoogland said U of T is working with MIT to come up with a way to electrically pump the nanocrystals, which would be necessary to create optical chips. Intel Research and other firms are also on top of the issue, he said.

“We’re still ahead of the problem,” he said. “We’re on the right track to reach this 2010 deadline.”

Nathan Brookwood, an analyst with Insight 64 in Saratoga, Calif., said Sun Microsystems and others are experimenting with laser interconnects on the motherboard and between computers, though it’s not necessarily their highest priority.

“The crisis du jour is power and thermals,” he said. “Interconnect speeds are less dire, although when we bump things up again (in microprocessor architecture), it will start to be a problem.”

The U of T team is developing considerable expertise in the use of nanotechnology for next-generation infrastructure issues. Two years ago, researchers from the same group proposed a way of using lasers to control fibre-optic networks, which they said could pave the way for devices that can perform a trillion operations rather than a billion operations per second.

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