Thomas Jens, Jovanovic Nemanja, Becker Ria G, Marshall Graham D, Withford Michael J, Tünnermann Andreas, Nolte Stefan, Steel M J
Friedrich-Schiller University, Institute of Applied Physics, Jena, Germany.
Opt Express. 2011 Jan 3;19(1):325-41. doi: 10.1364/OE.19.000325.
The spectral characteristics of a fiber Bragg grating (FBG) with a transversely inhomogeneous refractive index profile, differs considerably from that of a transversely uniform one. Transmission spectra of inhomogeneous and asymmetric FBGs that have been inscribed with focused ultrashort pulses with the so-called point-by-point technique are investigated. The cladding mode resonances of such FBGs can span a full octave in the spectrum and are very pronounced (deeper than 20dB). Using a coupled-mode approach, we compute the strength of resonant coupling and find that coupling into cladding modes of higher azimuthal order is very sensitive to the position of the modification in the core. Exploiting these properties allows precise control of such reflections and may lead to many new sensing applications.
具有横向非均匀折射率分布的光纤布拉格光栅（FBG）的光谱特性与横向均匀的光纤布拉格光栅有很大不同。研究了用所谓的逐点技术通过聚焦超短脉冲写入的非均匀和非对称FBG的透射光谱。此类FBG的包层模共振在光谱中可跨越整整一个倍频程，且非常明显（深度超过20dB）。我们采用耦合模方法计算共振耦合强度，发现耦合到更高方位阶次的包层模对纤芯中改性的位置非常敏感。利用这些特性可精确控制此类反射，并可能带来许多新的传感应用。
