Lasers + Silicon Wafers = Boost To Big Data

By fabricating tiny lasers directly on silicon wafers, researchers can integrate photonics with electronics, and with greater efficiency too.

AsianScientist (Jun. 10, 2016) – An international team of scientists from Hong Kong and the US has succeeded at fabricating tiny lasers directly on silicon—a significant finding for the semiconductor industry. They published their work in Applied Physics Letters.

For over 30 years, the crystal lattice of silicon and of typical laser materials could not match up, making it impossible to integrate the two materials. The group, led by researchers from the Hong Kong University of Science and Technology, has shown that integrating sub-wavelength cavities—the essential building blocks of their tiny lasers—with silicon enabled them to create high-density, on-chip light-emitting elements.

To show that the devices work as lasers, the group used a process called optical pumping, in which light, rather than electrical current, ‘pumps’ electrons from a lower energy level in an atom or molecule to a higher level.

“Putting lasers on microprocessors boosts their capabilities and allows them to run at much lower powers, which is a big step toward photonics and electronics integration on the silicon platform,” said corresponding author Professor Lau Kei May from the department of electronic and computer engineering at HKUST.

Traditionally, the lasers used for commercial applications are quite large at 1 x 1 mm. Smaller lasers tend to suffer from large mirror loss, where the laser beam loses energy with every bounce off of a mirror. But the scientists were able to overcome this issue with tiny whispering gallery mode lasers only one micron in diameter—that is, 1,000 times shorter in length and a million times smaller in area than those currently in use, according to Lau.

“Our lasers have very low threshold and match the sizes needed to integrate them onto a microprocessor,” Lau noted. “These tiny high-performance lasers can be grown directly on silicon wafers, which is what most integrated circuits, or semiconductor chips, are fabricated with.”

In terms of applications, the group’s tiny lasers on silicon are ideally suited for high-speed data communications.

“Photonics is the most energy-efficient and cost-effective method to transmit large volumes of data over long distances. Until now, laser light sources for such applications were ‘off chip,’ or missing from the component,” Lau explained.

“Our work enables on-chip integration of lasers, an [indispensable] component, with other silicon photonics and microprocessors.”



The article can be found at: Wan et al. (2016) Sub-wavelength InAs Quantum Dot Micro-disk Lasers Epitaxially Grown on Exact Si (001) Substrates.

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Source: American Institute of Physics; Photo: Shutterstock.
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