GILBERTO BRAMBILLA
1 μm
FIGURE 1. Two nanowires with radii of 30 and 50 nm manufactured from standard telecom optical fibers (around which they are entwined) are shown in a scanning-electron micrograph. (Courtesy of the University of Southampton)
Nanoscience and nanotechnology have
attracted much interest in recent years
because materials exhibit novel proper-
ties when structured at nanometer di-
mensions. In the last two decades, nano-
wires and subwavelength
wires have been fabricated from a variety of With large evanescent fields
materials using a wide range of techniques,
including electron-beam lithography, laser and high optical nonlinearity, Flame brushing
ablation, templates, vapor-liquid-solid tech- In the last four years, the
niques, physical- or chemical-vapor deposi- nanofibers drawn from manufacture of nano-
tion, and sol-gel. Although optical nanowires have optical fiber are well suited wires from optical fibers has been established as a
previously been fabricated from silica, most for optical sensors and other methodology to reliably
have exhibited an irregular profile along their produce structures with
length. Surface roughness and length inhomo- devices. Their standard-size a transmission loss low
geneity appear to have limited the loss levels enough to be used for op-
that could be reliably achieved, and thus their fiber ends allow for easy tical devices. Among the
usefulness for optical applications. top-down techniques, the
Nanowires can also be drawn from optical coupling of light in and out. “flame-brushing” tech-
fibers; this process results in very low surface nique provides the longest
roughness and high homogeneity. The low optical loss of and most uniform nanowires with the lowest measured loss.
these nanowires opens the way to a host of new optical de- Originally developed for the manufacture of fiber tapers and
vices for communications, sensing, biology, and chemistry. couplers, flame brushing is based on a small flame moving
Optical-fiber nanowires are fabricated by adiabatically under an optical fiber that is being stretched. The control of
the flame movement and the fiber stretch can be used to de-
fine the taper shape to an extremely high degree of accuracy.
Although taper diameters in the range of 1 μm can be eas-
stretching optical fibers, preserving the original fiber di-
mensions at the input and output ends and allowing ready
splicing to standard fibers and fiber components. These fiber
pigtails have macroscopic dimensions and allow the manip-
ulation of a single nanowire without the expensive instru-
mentation typical of the
nano world.
GILBERTO BRAMBILLA is a Royal Society Senior Research Fellow at the Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, England; e-mail: gb2@orc.soton.ac.uk.
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