Abstract
Narrow bandwidth and large group velocity $(v_{g})$
dispersion are two fatal limitations of slow light in Bragg fibers. In this paper, by introducing a well-designed
defect layer into the cladding of the Bragg fiber, the modal characteristics are modified by the coupling between
the core mode and the defect mode. The defect location mainly determines the coupling strength and, thus, exerts a
strong influence on $v_{g}$ and dispersion. The defect thickness
mainly determines the resonant wavelength of the defect waveguide and, thus, the wavelength where the modal coupling
takes place. Consequently, the two limitations of the slow-light propagation in the Bragg fiber are overcome through
proper optimization of the defect parameters. Around 1550 nm, a slow-light bandwidth up to 90 nm is achieved at an
average $v_{g}$ of $c/5$ ($c$ is the light velocity in a vacuum) under
$N = 2$, whereas an average
$v_{g}$ of $c/10$ is achieved with a bandwidth of
20 nm under $N = 5$. On the other hand, the slow-light
propagation of $v_{g} = 0.074c$ with both zero dispersion and
zero dispersion slope is achieved, which is able to support applications requiring a subterahertz bandwidth of
optical pulse. All of the fiber designs ensure sufficient low losses and good optical field distribution. The
results are helpful in developing various Bragg-fiber-based slow-light devices.
© 2007 IEEE
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