一种新型有效的侧面抽运耦合技术

A New Structure of Gold Diffraction Grating for Efficient SideCoupling of Double-Clad Fiber Laser

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.

Low coupling efficiency of transverse electric （TE） polarization waves by using binary gold diffraction gratings for side-coupling of double-clad fiber lasers is demonstrated theoretically. Meanwhile, a new multilayered structure for side-coupling of TE-polarization waves is proposed and the coupling efficiency as high as 72% is achieved by using three layers gold strips with different widths. And the higher efficiency with much more layers gold strips is predicted. The relationship between the line-width of multilayered gold grating and the efficiency of ＋1 and -1 order backward diffraction wave is analyzed.