Holey Fiber Supports Megawatt Pulses

Daniel S. Burgess

Scientists at Corning Inc. in Corning, N.Y., have developed a hollow-core photonic bandgap fiber that supports ultrashort pulses of infrared radiation with peak powers more than 100 times greater than those tolerated by conventional optical fiber. Such fibers promise applications across a variety of fields, including telecommunications.

The researchers produced the fiber by the stack-and-draw method, bundling capillaries to create a preform that they draw into a fiber while monitoring the exterior diameter of the pulled product. The fiber in cross section features a 12.7-µm-diameter central hole surrounded by eight rings of hexagonal airholes with a pitch of 4.7 µm, a structure that offers a transmission window from 1395 to 1510 nm and an attenuation of 13 dB/km at 1500 nm.

Working with a team at Cornell University in Ithaca, N.Y., the researchers investigated the performance of the material. In tests in air, the 3-m-long fiber transmitted 900-nJ, 110-fs pulses of radiation centered at 1470 nm. Spectral analysis of the output revealed that intrapulse Raman scattering shifted the wavelength of the pulses to approximately 1530 nm. When a 170-cm-long piece of the fiber was filled with xenon gas, it transmitted 470-nJ, 75-fs pulses of 1510-nm radiation with virtually no wavelength shift.

Karl W. Koch, a researcher on the team from Corning, explained that the performance of such photonic bandgap fibers makes them of particular interest for use in telecommunications. He said that the group has produced kilometer-long lengths of the fiber. Other applications might include their use in fiber amplifiers and lasers, multiphoton spectroscopy and photodynamic therapy. He predicted that the fibers will find a place in photonic components within two years and that they will be used for the transmission of optical telecom signals within five to 10 years.