Zou Fang, Liu Yunqi, Deng Chuanlu, Dong Yanhua, Zhu Shan, Wang Tingyun
Opt Express. 2015 Jan 26;23(2):1114-24. doi: 10.1364/OE.23.001114.
We demonstrate the fabrication of long-period fiber gratings (LPFGs) coated with high index nano-film using the atomic layer deposition (ALD) technology. Higher index sensitivity can be achieved in the transition region of the coated LPFGs. For the LPFG coated by nano-film with a thickness of 100 nm, the high index sensitivity of 3000 nm/RIU and the expanded index sensitive range are obtained. The grating contrast of the over-coupled LPFGs and conventional LPFGs are measured and the over-coupled gratings are found to have a higher contrast in the transition region. The cladding modes transition is observed experimentally with increasing surrounding index using an infrared camera. The theoretical model of the hybrid modes in four-layer cylindrical waveguide is proposed for numerical simulation. The experimental results are well consistent with theoretical analysis.
我们展示了使用原子层沉积（ALD）技术制造涂覆有高折射率纳米薄膜的长周期光纤光栅（LPFG）。在涂覆的LPFG的过渡区域可以实现更高的折射率灵敏度。对于涂覆有厚度为100nm的纳米薄膜的LPFG，获得了3000nm/RIU的高折射率灵敏度和扩展的折射率敏感范围。测量了过耦合LPFG和传统LPFG的光栅对比度，发现过耦合光栅在过渡区域具有更高的对比度。使用红外相机通过实验观察到随着周围折射率的增加包层模式的转变。提出了四层圆柱波导中混合模式的理论模型用于数值模拟。实验结果与理论分析非常一致。
