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Chinese researchers create advanced optical amplifier

July 13, 2015

A team of researchers has created a nanoscale device capable of amplifying fiber-optic signals 20 times more powerfully than previously-used devices, APS Physics reports.

As the world of IT starts to rely more heavily on optical signals—as opposed to electrical ones—scientists have been working to develop more advanced ways of guiding and amplifying light effectively.

Optical telecommunications technology uses a 1.54 micrometer standard wavelength; but until this latest innovation, amplifiers for near-infrared light have been bigger than a micrometer, meaning they cannot be used for integrated circuits.

Anlian Pan from China's Hunan University and Xiangfeng Duan of the University of California in Los Angeles have been working to develop a solution to this problem. Their team has designed an optical amplifier small enough to fit into an integrated circuit, meaning that it's ten times smaller than any device that came before it, but 20 times more powerful.

Based on an optical nanowire with a core-shell structure, the amplifier features a silicon core surrounded by a thick erbium/ytterbium silicone shell. The theory was that as light spread through the nanowire, the core-shell edge would contain most of the light, but a large amount would leak into the shell, where it would then be amplified.

However, this requires a delicate balance as the dimensions of both core and shell have to be selected precisely so that light is contained within the nanowire, but also transmitted to the outer shell to be amplified.

After a series of tests, the team found that the optimal design was a 300-nanometer-diameter core and a 150-nanometer-thick shell; amplifying light intensity by approximately 1000 times per millimeter of fiber.

The main conceptual development, Duan explains, lies in the flexibility of the design: "It allows us to tune the size of the core and shell independently, so we can simultaneously minimize the loss of light power and maximize the gain."

He believes that the amplifier will have a significant effect on the optics sector, influencing the next generation of on-chip optical communications components.

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