A joint team from Penn State University and the University of Southampton has made semiconductor devices, including a transistor, inside microstructured optical fibres. The resulting ability to generate and manipulate signals inside optical fibres could have applications in fields as diverse as medicine, computing, and remote sensing devices.



Optical fibre has proved to be the ideal medium for transmitting signals based on light, while crystalline semiconductors are the best way to manipulate electrons. One of the greatest current technological challenges is the rapid and efficient exchange of information between optics and electronics, and this new technique may provide the tools to cross the divide.

"This advance is the basis for a technology that could build a large range of devices inside an optical fibre," said John Badding, associate professor of chemistry at Penn State University. "While the optical fibre transmits data, a semiconductor device allows active manipulation of the light, including generating and detecting, amplifying signals, and controlling wavelengths."

The key breakthrough was the ability to form crystalline semiconductors that nearly fill the entire inside diameter, or pore, of very narrow glass capillaries. These capillaries are optical fibres - long, clear tubes that can carry light signals in many wavelengths simultaneously. When the tube is filled with a crystalline semiconductor (using chemical vapour deposition), such as germanium, the semiconductor forms a wire inside the optical fibre.

The team has built a simple in-fibre transistor, and they point to the success of the Erbium Doped Fiber Amplifier, invented in the late 1980s, to illustrate the transformational possibilities of this technology.

"At present you still have electrical switching at both ends of the optical fibre," says Badding. "If we can get to the point where the signal never leaves the fibre, it will be faster and more efficient. If we can actually generate signals inside a fibre, a whole range of optoelectronic applications become possible."

For more information contact John Badding, Penn State University, jbadding@pearl.chem.psu.edu