Abstract The effect of interstitial air holes on Bragg gratings in photonic crystal fibre (PCF) with a Ge-doped core is numerically investigated by using the beam propagation method (BPM). It is shown that the interstitial air holes (IAHs) can make Bragg resonance wavelength $\lambda _{\rm B}$ shift a little towards short wavelengths and increase $\lambda _{\rm B}-\lambda _{1}$ (the wavelength spacing between the main peak with Bragg resonance wavelength $\lambda _{\rm B}$ and the first side peak with wavelength $\lambda _{1})$ and the coupling coefficient $\kappa $ of Bragg resonance. Moreover, when the ratio of air hole diameter ($d$) to pitch (${\it\Lambda}$), $d/{\it\Lambda}$, is small, IAHs can suppress the cladding mode resonance. When $d/{\it\Lambda}$ is large, IAHs increase the number of mode that could strongly interact with the fundamental mode. By
comparing the transmission spectral characteristics of PCF-based fibre Bragg grating (FBG) with IAHs with those without IAHs at the same air-filling fraction, it is clarified that the change of transmission spectral characteristics of PCF-based FBG with IAHs is
not due to a simple change in air-filling fraction. It is also closely related to the distribution of interstitial air holes.
Received: 23 August 2007
Revised: 11 July 2008
Accepted manuscript online:
Fund: Project supported by the National
Natural Science Foundation of China (Grant No 10874145), and the
Yanshan University Doctoral Foundation (Grant No B153).
Cite this article:
Zhang Hui-Jia(张慧嘉), Li Shu-Guang(李曙光), and Hou Lan-Tian(侯蓝田) Effect of interstitial air holes on Bragg gratings in photonic crystal fibre with a Ge-doped core 2009 Chin. Phys. B 18 630
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