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|Document Type: ||Article|
|Title: ||AFM observation of surface topography of fibre Bragg gratings fabricated in
germanium-boron codoped fibres and hydrogen-loaded fibres.|
|Authors: ||Wei, C. Y.|
James, Stephen W.
Irving, Phil E.
Tatam, Ralph P.
|Issue Date: ||2002|
|Citation: ||C. Y. Wei, C. C. Ye, S. W. James, P. E. Irving and R. P. Tatam, AFM observation of surface topography of fibre Bragg gratings fabricated in germanium-boron codoped fibres and hydrogen-loaded fibres, Optical Materials, Volume 20, Issue 4, November-December 2002, Pages 283-294.|
|Abstract: ||This paper reports the measurement of the surface topology of optical fibres
containing a fibre Bragg grating (FBG) using an atomic force microscope (AFM).
The AFM observation was made on FBGs fabricated via the phase mask technique in
germanium–boron codoped optical fibres, in hydrogen-loaded germanium–boron
codoped fibres and in standard telecommunications optical fibres. The surface
images reveal that a spatial corrugation pattern was induced by the UV-
irradiation, with a period that is half of the period of the phase mask. This
UV-induced surface structure was found only on the side of the fibre facing
towards the incident UV-irradiation and did not appear on the rear surface. The
AFM probe scanned a 10×10 μm2 surface area at seven sites along the 6.0 mm
length of fibre that was exposed to the UV-irradiation. The amplitude of the
spatial corrugation pattern observed on the AFM image was quantified for each
site. It was found that the amplitude in a range of 0.7–3.2 nm was a function of
UV-laser intensity distribution and the type of fibre. Hydrogen loaded optical
fibres exhibited a corrugation with an amplitude twice as large as that observed
in the Ge–B doped fibres that were not hydrogen-loaded. This correlates with the
increase in photosensitivity produced by the hydrogen loading. A similar UV-
induced spatial corrugation was also observed on standard telecom fibres, but
without inducing the refractive index change in the fibre core. The observation
of surface topology provides an insight into the structural changes induced
during FBG fabrication. UV-induced densification and laser ablation could
account for the formation of the surfac|
|Appears in Collections:||Staff publications - School of Engineering|
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