金属包层长周期光纤光栅的理论和实验研究

金属包层长周期光纤光栅可用于对谐振波长的调谐。通过实验和理论研究了长周期光纤光栅在沉积金属包层前后谐振波长的变化规律。分析了金属包层光纤的特点，给出了金属包层光纤包层模的本征方程，并给出了这一复本征方程的求解方法。长周期光纤光栅在沉积金属包层后，对低阶包层模，谐振波长会向长波方向偏移，模次增加，偏移会增大；对高阶包层模，谐振波长向短波方向偏移。不同金属包层，谐振波长的偏移量也有一定差别。所给出的理论分析方法，可用于预测谐振波长的偏移方向和大小，对设计和制做这类长周期光纤光栅提供理论参考。

Theoretical and Experimental Investigation of Metal-Coated Long-Period Fiber Gratings

Metal coated long period fiber gratings (LPFG) can be used to change the resonance wavelength. The shifting characteristics of the resonance wavelengths of LPFG before and after the metal clad is deposited on the fiber are investigated theoretically and experimentally. The eigenvalue equation for the cladding modes of the metal coated fiber is obtained and the method of solving the complex eigenvalue equation is presented. When metal clad is deposited on the long\|period fiber grating, for the lower order cladding modes, the resonance wavelength shifts to longer side. With the increase of the mode order, the shift becomes greater. For the higher order cladding modes, the resonance wavelength shifts to shorter side. The shift of the resonance wavelength has some difference for different kinds of metal. The theoretical method presented here can be employed to forecast the shift of the resonance wavelength, and to help the design and fabrication of the metal coated LPFG.