CAJ | 학술논문

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HE_(1,2)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HE_(1.6)),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HE_(1.14)).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.
침대도고절사솔납미막적장주기광책,건립료전감이론모형,연구료장주기광책적해진파장여납미막후도급외계절사솔적관계,급출불동납미막후도하장주기광책불동포층모식중조특성.연구발현,당장주기광책외면도상일층연각향균균분포적납미막시,수착막후변화회출현포층모분포적명현조제;괄당선택도막삼수화외계개질절사솔,최저차포층모식HE_(1,2)회성위도막층중적도모,기타적포층모식장회발생모식전환현상;대우교저차포층모식(여HE_(1.6)),재모식전환적시후존재량보전환,이고차적포층모지유일보전환(여HE_(1.14)).동시급출료포층모식전환대외계절사솔향응적관계:당막층후도증가시,장주기광책모식전환현상이지저절사솔구역.
The sensing theoretical model of long-period gratings (LPGs) with high-refractive-index nanometer film coating is built. The influence of overlay thickness and external refractive index on the resonant wavelength of LPG is investigated theoretically. The phenomenon of reorganization of cladding modes at different coating film thicknesses is shown and explained in detail. The theoretical analysis shows that a significant modification of the distribution of cladding modes is seen as an azimuthally symmetric nanoscale high-refractive-index coating deposited on the cladding of LPG. If the parameters of layers (the refractive index and thickness) and the external refractive index are chosen accurately, the lowest cladding mode HE_(1,2) will become the overlay mode and other cladding modes will experience mode transition. For the lower cladding modes (such as HE_(1,6)), there is two-step modes transition. For higher cladding modes(such as HE_(1,14)), there is only the one-step modes transition. The mode transition on the sensitivity of the external refractive index is also analyzed: Modes transition shifts to lower refractive index region with the increase of the overlay thickness.