全光纤光子轨道角动量模式的产生

通过模分复用技术，将带有不同阶数轨道角动量的光波作为不同的信道，能够从另一维度极大的增加光通信的容量。光子轨道角动量的产生是这类技术的一个核心。我们基于有效介质理论，在光纤端面设计了特殊的螺旋结构，使光纤端面的有效折射率沿着顺时针或逆时针方向线性增加。当传导光波入射到该结构时，会因为方位角上的折射率不同而形成光程的差异，从而引起相应的相位延迟并形成相位波前的螺旋形结构，即产生带有轨道角动量的光波,我们使用FDTD方法模拟了轨道角动量的产生过程。

Research on the All Optics Fiber Generator of Orbital Angular Momentum Beam

Light waves with orbital angular momentum (OAM) can be applied in the mode division multiplexing technology, which offers a new way to enlarge the communication capacity from another dimension. The generation of the OAM is the key of this technology. Based on the effective medium theory, we designed a special structure at the end of the optical fiber: vortex structures which make the effective refractive index increases clockwise or counter-clockwise. When the incident light goes through this structure, the different refractive index will cause the different optical path and the corresponding phase delay alone the azimuthal angle, i.e. the OAM light. The above OAM generation process is simulated using an FDTD software.