Electronic function built into optical fibre

A joint team from the University of Southampton in Britain and Penn State University in the US has combined the technologies of optical fibre and silicon/germanium to make devices inside microstructured fibres.

The team has made a transistor and the resulting ability to generate and manipulate signals inside optical fibres could have applications in fields as diverse medicine, computing and remote sensing devices.

Optical fibre has proved to be a suitable 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 exchanging information between optics and electronics rapidly and efficiently. This new technique may provide the tools to cross the divide.

"This is the basis for technology that could build a large range of devices inside an optical fibre," said John Badding, associate professor of chemistry at Penn.

"While the optical fibre transmits data, a semiconductor device allows active manipulation of the light, including generating and detecting, amplifying signals and controlling wavelength. If the signal never leaves the fibre, then it is faster cheaper and more efficient."

"This fusion of two technologies opens the possibility of true optoelectronic devices that do not require conversion between optical and electronic signals," said Pier Sazio, senior research fellow in the Optoelectronics Research Centre at Southampton.

"If you think of the fibre as a water main, this structure places the pumping station inside the pipe. The fibre provides the transmission and the semiconductor provides the function."

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, such as germanium, the semiconductor forms a wire inside the fibre.

The combination of optical and electrical capabilities provides the platform for development of new optoelectronic devices.