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Texan scientists create tiny, tiny laser

Boon for on-chip optics

The University of Texas at Austin has unveiled a laser built from a 28 nanometer rod and a 5 nm silicon dioxide layer.

Despite the diminutive dimensions, the laser offers a lengthy stride It is, however, offering a good step forward in using optical communications between and within electronics. One of the challenges for a designer wanting on-chip optics is that optical components are generally bigger than the electronics they support.

The problem is more fundamental than component size: rather, it’s about the scale of light waves and how they behave – in particular, the way that surface irregularities scatter the light (which influences what’s known as the 3D diffraction limit).

The university has spent 15 years working on this problem, and has published a paper in Science (abstract) claiming to have developed a nanoscale laser that operates “well below the 3D diffraction limit”, according to physics professor Ken Shih.

The tiny laser uses a gallium nitride nanoscale rod partly filled with indium gallium nitride. This sits on a silicon insulator covering a silver film described as being “smooth at the atomic level”.

That smoothness, the scientists say, is what protects the resulting plasmon beam from scattering.

Replacing on-chip electronic communication with optical paths reduces the amount of heat that the chip generates. Heat build-up is one of the factors that boffins have to overcome if they’re to keep chips merrily following Moore’s Law for a few years longer – since as features get smaller, they cram more heat-generating components into a smaller space.

On-chip optics would leave more of a chip’s “heat budget” available for the transistors that do the work – but only if you can create optical features whose size is suitable for fabricating into the chip. ®

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