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抽运耦合技术是获得高功率激光器的关键技术之一.针对国外最新提出的一种利用二元金属衍射光栅进行侧面抽运耦合双包层光纤(DCF)激光器的方法,利用严格的矢量衍射理论,证明了这种二元金属衍射光栅虽然对TM偏振模有近94.4%的衍射效率但是对TE偏振模最大只有35%的衍射效率,因此对入射光存在严重的偏振依赖性.在综合考虑了对不同入射偏振光均具有较高衍射效率以及多层金属衍射光栅的工艺制作难度的前提下,提出了一种新型的三层阶梯状的金属光栅结构,该结构对入射的TE偏振光最大能达到72%的耦合效率,并且对TM偏振也保持较高的耦合效率,而且随着阶梯层数的增加,耦合效率将进一步增大.同时给出了金属衍射光栅的周期与厚度对+1阶和-1阶后向衍射波的衍射效率的影响.
Pumping coupling technology is one of the key technologies to obtain high power laser.According to the newly proposed method of side-pumping double-clad fiber (DCF) laser using binary metal diffraction grating, a new method based on strict vector diffraction theory , It is proved that the binary metal diffraction grating has a serious polarization dependence on the incident light though it has a diffraction efficiency of nearly 94.4% for the TM polarization mode but only a maximum of 35% for the TE polarization mode, Based on the high diffraction efficiency of different incident polarized light and the difficulty in fabrication process of multi-layer metal diffraction grating, a novel three-layer stepped metal grating structure is proposed. The structure can maximize the incident TE polarized energy The coupling efficiency reaches to 72%, and the coupling efficiency of TM polarization is also kept high, and the coupling efficiency will further increase with the increase of the number of layers, and the relationship between the period and the thickness of the metal diffraction grating to the + 1st order And the diffraction efficiency of -1 order backscattered waves.