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2
Centre for Optical and Electromagnetic Research and Department of Physics,
show its length. The maximum diameter variation DD is about 8 nm
Zhejiang University, Hangzhou 310027, China
over the 4-mm length L of the wire, giving DD/L ¼ 2 £ 1026. The
3
Department of Physics, Graduate School of Science, Tohoku University, Sendai,
excellent uniformity of wires with diameters ranging from 50 to
Miyagi 9808578, Japan
1,100 nm can also be seen in Fig. 2b d. Higher-magnification
* Present address: Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, Massachusetts
transmission electron microscope (TEM) images of a 240-nm-
02420, USA
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Silica waveguides with diameters larger than the wavelength of
transmitted light are widely used in optical communications,
sensors and other applications1 3. Minimizing the width of the
waveguides is desirable for photonic device applications, but the
fabrication of low-loss optical waveguides with subwavelength
diameters remains challenging because of strict requirements on
surface roughness and diameter uniformity4 7. Here we report
the fabrication of subwavelength-diameter silica  wires for use as
low-loss optical waveguides within the visible to near-infrared
spectral range. We use a two-step drawing process to fabricate
long free-standing silica wires with diameters down to 50 nm that
show surface smoothness at the atomic level together with
uniformity of diameter. Light can be launched into these wires Figure 1 The second step in the fabrication process of silica submicrometre- and
by optical evanescent coupling. The wires allow single-mode nanometre wires (SMNWs). a, Schematic diagram of the drawing of the wire from a coil of
operation, and have an optical loss of less than 0.1 dB mm21. micrometre-diameter silica wire wound around the tip of a sapphire taper. The sapphire
taper is heated with a CH3OH torch with a nozzle diameter of about 6 mm. The wire is
We believe that these wires provide promising building blocks for
future microphotonic devices with subwavelength-width drawn in a direction perpendicular to the sapphire taper. b, Magnified view of the drawing
structures. process. The sapphire taper ensures that the temperature distribution in the drawing
region remains steady.
The fabrication of thin silica wires was first investigated in the
816 NATURE | VOL 426 | 18/25 DECEMBER 2003 | www.nature.com/nature
© 2003 Nature Publishing Group [ Pobierz caÅ‚ość w formacie PDF ]
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