January 17, 2008, Bath, UK--Researchers at the University of Bath have discovered a way of speeding up the production of hollow-core optical fibers. The procedure, described in Optics Express (vol. 16, issue 2, pp. 1142-1149), cuts the production time of these fibers from around a week to a single day, reducing the overall cost of fabrication.
According to Prof. Jonathan Knight from the Centre for Photonics & Photonic Materials in the Department of Physics at the university, initial tests show that the fiber is also superior in virtually every respect to previous versions of the technology, making it an important step in the development of new technologies that use light instead of electrical circuits to carry information. These technologies include faster optical telecommunications, more powerful and accurate laser machining, and the cheaper generation of x-ray or ultraviolet light for use in biomedical and surgical optics.
"This is a major improvement in the development of hollow-core fiber technology," Knight says. "In standard optical fibers, light travels in a small cylindrical core of glass running down the fiber length. The fact that light has to travel through glass limits them in many ways. The glass can be damaged if there is too much light, and the glass causes short pulses of light to spread out in a blurring effect that makes them less well defined. This limits its usefulness in telecommunications and other applications.
The problem in developing hollow-core fibers is that only a special sort of optical fibre can guide light down an air hole. They use a two-dimensional pattern of tiny holes in the glass around the core to trap the light within the core itself. The highly detailed nature of these fibers means that they have been difficult to fabricate and they can only work for a limited range of wavelengths.
However, the new procedure developed by the Bath photonics group shows how a tiny change to these fibers--narrowing the wall of glass around the large central hole by just a hundred nanometers--broadens the range of wavelengths which can be transmitted. They achieved this by omitting some of the most difficult steps in the fabrication procedure, reducing the time required to make the fibers from around a week to a single day.
The superior performance of the fiber means that it could have a significant impact in a range of fields such as laser design and pulsed beam delivery, spectroscopy, biomedical and surgical optics, laser machining, the automotive industry and space science.
"For biomedical research, we can use these fibers to deliver light for diagnosis or surgery anywhere – even deep inside the body," Knight says. "Almost any device where light is important or can be used, photonic crystal fibres can make more efficient, sensitive and powerful."