Design Of Coupling System Based On CWGIF

With the development of optical devices and semiconductor laser,optical fiber communication plays an increasingly important role.As the main source of optical fiber communication,semiconductor lasers are key devices,however,they have an asymmetric elliptical spot with large divergence angles,that is a big problem and impedes the application of semiconductor laser.Therefore,how to improve the coupling efficiency between semiconductor and single mode fiber attracts more and more attention of researchers.This thesis presents a design of coupling system based on cylindrical wedge-shaped graded index fiber(CWGIF),and the main contents are summarized as the followings:(1)According to knowledge of Principle of Laser,Applied Optics and Fiber Optics,we analyzed CWGIF coupling system theoretically.Then,the initial structural parameters are calculated.(2)Models for the semiconductor laser and CWGIF coupling system are built in ZEMAX based on Physical Optics Propagation(POP)module and user-defined surface method,respectively.Models for the semiconductor laser and CWGIF coupling system are built in BeamPROP based on method of communicating with ZEMAX and user-defined polygons method,respectively.(3)CWGIF coupling system is optimized to achieve smaller spot by using ZEMAX.Then,coupling efficiency of optimized CWGIF coupling system is calculated by using Beam Propagation Method(BPM)in BeamPROP.(4)The tolerances of CWGIF coupling system are analyzed and discussed by changing decenter between semiconductor laser and CWGIF coupling system in different directions.In addition,the changes of coupling efficiency with different aspect ratios of elliptical spot are analyzed and discussed.