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研究了轨道角动量(OAM)模式在柚子型微结构光纤(MOF)中的传输。光纤纤芯周围存在一层直径为3μm的柚子型空气孔,由于空气孔与光纤纤芯之间存在较大的折射率差,传输的光被局限在纤芯中,从而形成稳定的传输模式。通过有限元法对光纤中的矢量本征模式进行模拟,得到了模式的有效折射率和模场分布。结果表明,MOF在630nm波长附近可支持10个OAM模式传输,各模式间的有效折射率差达到0.01以上,较大的有效折射率差可抑制光纤中各模式间的相互耦合,从而提高OAM模式在光纤中的传输性能。实验中利用特殊设计的光学旋涡达曼光栅对在光纤中传输1m的OAM_(1,1)和OAM_(-1,1)模式进行解调。
The transmission of orbital angular momentum (OAM) mode in grapefruit-type microstructured optical fiber (MOF) was studied. There is a grapefruit-type air hole with a diameter of 3μm around the fiber core. Due to the large refractive index difference between the air hole and the fiber core, the transmitted light is confined in the fiber core to form a stable transmission mode. Through the finite element method to simulate the vector eigenmodes in optical fiber, the mode effective refractive index and mode field distribution are obtained. The results show that MOF can support 10 OAM modes near 630nm wavelength and the effective refractive index difference between the modes is above 0.01. The larger effective refractive index difference can suppress the mutual coupling between the modes in the optical fiber and improve the OAM mode Transmission performance in optical fiber. In the experiment, a specially designed optical vortex dman grating was used to demodulate OAM_ (1,1) and OAM_ (-1,1) modes transmitting 1m in optical fiber.