Silicon optical fiber made practical
"In essence, we've married optoelectronics with optical fibers," said Ballato. "In the past, we've needed one structure to process light and another to carry it. With a silicon fiber, for the first time, we have the ability to greatly enhance the functionality in one fiber."
Usually an optical fiber is made by starting with a glass core, wrapping it with a cladding made from a slightly different glass, and then heating the structure until it can be pulled out into long wires. This works well enough, but for some wavelengths of light, a core made of pure crystalline silicon, like the one developed by the Clemson team, would better carry signals. Additionally, crystalline silicon exhibits certain nonlinear properties (in which the output is not proportional to the input) that are many orders of magnitude larger than for conventional silica glass. This would, for example, allow for the amplification of a light signal or for the shifting of light from one wavelength to another. The development of a silicon fiber opens the way for signal processing functions that are currently done electronically or in separate optical circuits to be performed directly inside the fiber, which allows for more compact, efficient systems.
Some fibers have been made with a silicon core, but the Clemson version (with collaborators at UCLA, Northrop Grumman and Elmira College) is the first to employ standard mass-production methods, bringing them closer to commercial reality.
Right now the amount of energy lost when the lightwaves move down this silicon fiber is no better than for other fibers at the longer wavelengths, but Ballato says that the work so far has been a proof-of-concept, and he expects energy losses to decline signficantly with continued optimization.
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