The Design And Performance Analysis Of OAM Mode Generator Based On SOI Strip Waveguides

In recent years,with the rapid development of the Internet,the demand for communication capacity has been increased continuously.The existing optical fiber communication system can't meet people's requirements.As a new emerging technology,Orbital Angular Momentum?OAM?provides a potential solution.Compared with traditional optical communication,the beam carrying OAM has new degrees of freedom,which makes the OAM multiplexing technology have unique advantages in improving the channel capacity and spectrum utilization of the system.In order to realize OAM multiplexing communication,the primary problem is to generate OAM vortex beams.At present,the existing methods of generating OAM beams have some problems,such as large size,non-planar and complex system.It is difficult to be integrated to meet the requirements of OAM optical communication system.In this paper,we present a silicon OAM generator,which is easy to be integrated.The device consists of two parallel waveguides and a phase shifter composed of strip waveguides.Firstly,the generation method and principle of optical orbital angular momentum are analyzed.On this basis,the coupling structure and phase shifter structure are designed.Then,the effects of different structural parameters on the performance of OAM generator are analyzed.By adjusting the width and coupling length of the waveguides and changing the length and position of trench,We optimize and analyze the properties by the finite difference time domain?FDTD?method.The results show that the optimized OAM generator can realize the generation ofOAM_?1.It has a compact structure with footprint of 33?m×2?m and low loss?<0.16 dB?,and the mode conversion efficiency is over 97%.The fabrication process is simple and easy to integrate.The device can be used in OAM multiplexing optical communication,and has important application value for improving the capacity of optical communication system.