具轨道角动量光束用于光通信编码及解码研究

Research on the Beam with Orbital Angular Momentum Used in Encoding and Decoding of Optical Communication

无衍射光是在自由空间传播过程中一定范围内横向强度分布保持不变的光场,具有方向性好以及传输距离远等特点,某些类型的无衍射光具有轨道角动量。分析了具有轨道角动量光束以及无衍射光在空间中的传输特点,以计算全息图作为反射式相位调制的空间光调制器(SLM)实现光学变换,并通过由锥形透镜构成的模式转换器,将携带信息的拉盖尔-高斯(L-G)光束转换成为具有相同拓扑荷的高阶Bessel无衍射光束,提出了一种通过具有轨道角动量的高阶Bessel无衍射光束来进行空间光信息传输的编码解码方法,在保证激光大气通信的安全保密性的同时,提高了信息传输的密度和准确率。

Non-diffracting beams possess advantages of better direction and far distance for applications to free-space communications. During free propagation, their profiles of transverse intensity remain nearly invariant in a range. Some non-diffracting beams have orbital angular momentum. By analyzing the characteristic of the beam with orbital angular momentum and non-diffracting beams transmission, the computer-generated hologram was used as spatial light modulator with reflective phase modulation to implement optical transformation. Laguerre-Gaussian beam carrying the information is transformed to a higher-order Bessel non-diffractive beam with the same topological charge by a mode converter consistina of axicon. A method of encoding and decoding of optical communication was proposed based on the non-diffracting high-order Bessel beams with orbital angular momentum. The proposed approach not only ensures the security of atmospheric laser communication, but also improves the density and precision of information transmission greatly.