Researchers from Clemson University are bringing ordinary materials to unordinary places by converting readily obtainable and affordable materials into sapphire optical fiber. We have now reached the point where there is so much light packed in fiber cables that the silica material used to manufacture it fundamentally can’t handle the intensity and has begun interacting and working against us, via phenomenon like Brillouin scattering.
“We have used a highly purified version of beach sand (silica) for fiber for the last 40 years. As a matter of fact, the 2009 Nobel Prize in Physics was awarded for the development of silica optical fibers. However, while silica has done remarkably well over time, it is now being pushed to its limits for faster and cheaper data and new functionality,”
says John Ballato, director of the Center for Optical Materials Science and Engineering Technologies at Clemson University.
“At high power, the light causes the atoms of the material to vibrate more violently and those vibrations convert some of the light energy into sound energy which restricts the ability of the fiber to carry more power,” said Ballato. “This, in turn, lessens the amount of light that can travel through the fiber, which limits the amount of information that can be sent for telecommunications uses and power for high-energy laser applications.”
The need for stronger and more durable fiber material is greater than ever before and will only increase with technological advancement. Clemson researchers are focusing on providing a materials-based solution for fiber optics data saturation, particularly one that can be sold commercially. The goal is to take a robust, affordable, and easily accessible material that can take the brunt of greater intensity and convert that material into a fiber.
Why Sapphire?
The researchers discovered that sapphire possesses some unusual properties that make it valuable for high power lasers in which the light intensity interacts with sound waves in the glass and leads to diminished power-handling capabilities. Sapphire is transparent from UV wavelengths to Infrared. It is 5 times stronger than ordinary glass, and much tougher than tempered glass.
Sapphire is combined with composites to fabricate shatter resistant windows used in armored vehicles and various military body armor suits. Some xenon arc lamps employ sapphire windows to tolerate higher thermal loads and thus higher output powers.
“Sapphire is new and different in this sense because we’re able to use a low-cost and widely used commodity as a fiber,” explains Ballato. “Sapphire is scalable, acceptable and is a material that people don’t think about when it comes to fiber optics. The problem is that sapphire’s crystalline structure is not amenable to making into optical fiber using commercially accepted methods.”
In fact, Ballato developed the sapphire optical fiber to endure greater intensity and be more useful for high-energy applications than typical commercial fibers, such as military grade fiber-laser systems.
“This research is paving the way for everyday commodities to be imagined for technological uses such as fiber optics. We’re performing additional studies with sapphire and other materials that have similar effects for fiber,”
Ballato said.
“Ballato’s recent results with sapphire fibers represent a paradigm-shifting development in the field of fiber optics. Materials long considered to be used only in the realm of free-space optics can now be exploited in fiber geometries, which enable long interaction lengths and novel nonlinear optical effects,”
said Siddarth Ramachandran, associate professor in the electrical and computer engineering at Boston University.
Sapphire-derived all-glass optical fibres P. Dragic, T. Hawkins, P. Foy, S. Morris & J. Ballato Nature Photonics doi:10.1038/nphoton.2012.182
