Paint-on lasers promise faster chip future

Quantum engineering with a hairdryer may prove the solution to a chip problem that's still ten years away

Researchers at the University of Toronto have produced a new form of laser that can be made by painting surfaces with a liquid.

In an announcement made earlier this month, the researchers claimed the development could lead to very fast chip interconnections circumventing a future barrier to faster computer designs.

"We've made a laser that can be smeared onto another material," said Professor Ted Sargent, a research chair in nanotechnology at the university, in a statement. "This is the first paint-on semiconductor laser to produce the invisible colours of light needed to carry information through fiber-optics. The infrared light could, in the future, be used to connect microprocessors on a silicon computer chip."

Electrical interconnects suffer from various physical problems of mutual interference and increasing resistance that get worse as the devices get smaller and faster. Intel has previously said that above around 10GHz signalling speed, copper interconnects may stop being viable — a frequency that is expected to be reached in around ten years' time. Lasers have the potential to work much faster with fewer problems, provided they can be integrated effectively with the electronics of the silicon chip.

The University of Toronto laser uses nanoparticles which are tiny motes of dust that are akin to customised atoms and that can be suspended in a liquid like particles in paint. Like the constituents of paint, they can be made to be particularly active at certain colours, with the electronic configuration of the particles additionally set up to absorb and emit photons in a way capable of supporting laser light production.

""We crystallised precisely the size of the nanoparticles that would tune the colour of light coming from the laser. We chose nanoparticle size, and thus colour, the way a guitarist chooses frets to select the pitch of the instrument," researcher Sjoerd Hoogland said. "Optical data transfer relies on light in the infrared — light with a wavelength roughly 1.5µm that travels further in glass than light of other frequencies. We made our particles just the right size to generate laser light at exactly this wavelength."

Once painted onto the right structure and allowed to dry — in demonstrations, the researchers have used a miniscule glass tube and a hairdryer — the dots form a device that will emit laser light if pulsed with ordinary light in the right way. The results are good, claim the researchers, with the light being particularly insensitive to variations in frequency caused by temperature.