基于Kagome结构光子晶体光纤的微孔型光栅谐振耦合与敏感机理研究

Lengths of gas/liquid devices based on hollow-core photonic bandgap fibers are always on the order of several tens of centimeters, whereas the diameter of the fiber core is only on the order of 10 μm. Thus the infiltration of gas or liquid into the fiber core is difficult and time-consuming, which limites the application of these devices and sensors seriously. Based on the Kagome-lattice photonic crystal fiber, we propose an idea of strongly perturbed microhole-structured fiber gratings, of which the coupling mechanism and applications should be investigated, to overcome the problems existed with the photonic bandgap fiber based gas/liquid devices and sensors. Microholes in the fiber grating act as microchannels that enabling the infiltration of gases, as well as the strong modulation of the grating that forming the lossy dips in the transmission spectrum. Detail works are listed below: (1) establishing the coupled local-mode theory and the transmission spectrum calculation method of the microhole-structured gratings in Kagome-lattice photonic crystal fiber; (2) efficient femtosecond laser fabrication of microhole-structured gratings in Kagome-lattice photonic crystal fiber with high quality; and (3) investigation on the sensing characteristics of the Kagome-lattice photonic crystal fiber based microhole-structured grating in pressure and hydrogen concentration measurement.

基于空芯带隙型光子晶体光纤的气体/液体器件往往具有数十厘米以上的长度，而纤芯直径仅为10微米左右，因此气体或液体进入纤芯的实现难度大，且响应时间很长，严重制约了这类器件和传感器的应用。为了有效解决这些问题，我们基于Kagome结构光子晶体光纤创造性地提出微孔光栅结构并对其强调制耦合机理及应用进行研究，微孔光栅中的微孔既能够作为气体进出光纤的微通道，同时又作为形成光栅的周期性强调制，在透射光谱中形成损耗峰。具体拟开展以下研究工作：（1）针对Kagome结构光子晶体光纤中的微孔光栅，建立相应的局部耦合模理论和透射谱计算方法；（2）实验研究Kagome结构光子晶体光纤中微孔光栅的飞秒激光高质高效制备；（3）基于Kagome结构光子晶体光纤微孔光栅，实验研究其在气压、氢气浓度监测等方面的传感特性。

光子晶体光纤器件通常具有极不协调的长度-孔径比，特别是纤芯直径仅为10微米左右，因此导致待测气体/液体进入纤芯并与光场相互作用的难度大、响应时间很长，严重制约了光子晶体光纤器件的应用。为了有效解决这些问题，本项目提出采用具有较大空气孔径的Kagome结构光子晶体光纤制备微孔光栅器件并对其强调制耦合机理及应用进行研究，此类器件中的光栅微孔既能够作为待测物微通道，又同时作为强调制光栅的基本单元，能够实现一类新颖的高灵敏度、快速响应光子晶体光纤传感器件。本项目针对Kagome结构光子晶体光纤中的微孔光栅的局部耦合模理论和透射谱计算方法、微孔光栅的飞秒激光高质高效制备方法、微孔光栅传感特性与应用展开了深入研究，分析了Kagome结构光子晶体光纤空气孔几何尺寸、结构排布等参数对导模色散特性的影响，优化设计了在可见光和C波段同时具有较宽带隙的Kagome型光子晶体光纤，掌握了Kagome结构光子晶体光纤微孔光栅的飞秒激光制备方法，获得了一系列具有极高灵敏度的新颖光子晶体光纤传感器，如灵敏度高达2.39 nm/kPa的气压传感器、灵敏度高达208 nm/( rad•mm-1)的扭转传感器、灵敏度高达9.56 nm/Vrms的电场传感器等，相关结果已在Optics Letters、Optics Express、Nanoscale等刊物上发表28篇SCI论文。本项目的顺利开展对光纤传感技术的发展具有积极地推动作用，特别是为新型光子晶体光纤传感器件的设计、制备及应用提供了一种简单思路。