Del Villar Ignacio, Matias Ignacio R, Arregui Francisco J
Departamento de Ingeniería Eléctrica y Electrónica, Universidad Pública de Navarra, 31006 Pamplona, Spain.
Opt Lett. 2005 Sep 15;30(18):2363-5. doi: 10.1364/ol.30.002363.
It was proved [Opt. Lett. 30, 720 (2005)] that the deposition of an overlay of higher refractive index than that of the cladding on a long-period fiber grating (LPFG) causes large shifts in the attenuation bands induced by the grating. The result is an enhancement of the sensitivity of the LPFG to variations in the ambient and overlay refractive indices or the overlay thickness. The limitation of the previous design to materials with higher refractive indices than that of the cladding of the LPFG is overcome with a five-layer model. To this purpose, a first overlay of higher refractive index than that of the cladding of the LPFG will enhance the sensitivity of the device to variations in the refractive index of a second overlay of lower refractive index than that of the cladding of the LPFG. Moreover, it is proved that, if the second overlay is thick enough, its behavior resembles that of an infinite layer.
[《光学快报》30, 720 (2005)] 证明，在长周期光纤光栅 (LPFG) 上沉积折射率高于包层的覆盖层会导致光栅引起的衰减带发生大幅偏移。结果是增强了LPFG对环境和覆盖层折射率或覆盖层厚度变化的灵敏度。五层模型克服了先前设计对折射率高于LPFG包层的材料的限制。为此，折射率高于LPFG包层的第一覆盖层将增强该器件对折射率低于LPFG包层的第二覆盖层折射率变化的灵敏度。此外，证明了如果第二覆盖层足够厚，其行为类似于无限层的行为。
