论文部分内容阅读
针对镀高折射率纳米膜的长周期光栅,建立了传感理论模型,研究了长周期光栅的谐振波长与纳米膜厚度及外界折射率的关系,给出不同纳米膜厚度下长周期光栅不同包层模式重组特性。研究发现,当长周期光栅外面镀上一层沿角向均匀分布的纳米膜时,随着膜厚变化会出现包层模分布的明显调制;适当选择镀膜参数和外界介质折射率,最低次包层模式HE1,2会成为镀膜层中的导模,其他的包层模式将会发生模式转换现象;对于较低次包层模式(如HE1,6),在模式转换的时候存在两步转换,而高次的包层模只有一步转换(如HE1,14)。同时给出了包层模式转换对外界折射率响应的关系:当膜层厚度增加时,长周期光栅模式转换现象移至低折射率区域。
Aiming at the long period grating with high refractive index nanometer film, a sensing theoretical model was established. The relationship between the resonant wavelength and the thickness of the nanometer film and the refractive index of the outer layer was studied. The long period grating with different nanometer film thickness Layer mode recombination characteristics. It is found that when a long period of grating is coated with a layer of nanofilms evenly distributed along the angle, a significant modulation of the cladding mode distribution occurs along with the change of the film thickness. Appropriate choice of the coating parameters and the refractive index of the outer medium, Layer mode HE1, 2 will become the coating in the guide mode, the other cladding mode will occur mode conversion phenomenon; for the lower sub-cladding mode (such as HE1,6), there are two-step conversion mode conversion, The high-order cladding mode only one step conversion (such as HE1,14). At the same time, the relationship between cladding mode transition and external refractive index response is given. When the film thickness increases, the long-period grating mode transition phenomenon moves to the low refractive index region.