Research On Coupling Law And Alignment Algorithm Of Silicon Grating Coupler And Fiber

In the era of rapid development of artificial intelligence and 5G,people have higher and higher requirements on the capacity and speed of data processing.In many fields of data communication,optical interconnection technology is needed for huge data exchange,and the integration of optical interconnection has been a hot research topic in recent years.Silicon photonics have been widely studied for its superior performance,and the technology of silicon photonics is becoming more and more mature,and many high-performance silicon based devices have emerged.Among them,the high-performance devices that can realize the coupling function between the chip and the fiber are very important,which is one of the key devices that embody the commercial value of optical integrated chip.Grating couplers have the advantages of easy fabrication,high flexibility,large alignment tolerance,etc.,and become the most important solution to solve the coupling problem between chip and fiber.In this paper,the grating coupler is the focus of the study.Firstly,the optical characteristics of the coupler are studied.The results show that the main factors affecting the coupling efficiency of the chip and the fiber are the grating structure parameters and the fiber alignment error.Then,the optical model and coupling alignment system are constructed,and the coupling law and coupling algorithm are studied.The specific work is as follows:(1)Based on Bragg diffraction conditions,the working principle of the grating coupler was analyzed,and the optical model was constructed to analyze the propagation characteristics of the light field.The effect of grating key parameters on diffraction characteristics was analyzed by simulation.The results show that the etching depth has a significant effect on the diffraction intensity of grating,and the period mainly affects the diffraction order.The difference between single mode fiber and grating coupler is compared by mode field simulation,which lays a foundation for coupling simulation and experiment.(2)Based on the coupling theory of Gaussian beam and waveguide grating,the abstract mathematical model of the coupling process is studied.The coupling model of grating coupler and single-mode fiber was established and the coupling law was analyzed.Based on the simulation data,the overall design of the coupling alignment system is completed,the coupling law is verified by experiments,and the possible error loss sources in application scenarios are analyzed,which provides a reliable reference for automatic wafer testing.(3)Based on the self-developed coupling alignment system,the coupling alignment algorithm of single mode fiber and grating coupler is studied.According to the coupling law,the optimization strategy of rough alignment algorithm based on helical scanning method is proposed.In fine alignment algorithm research,in view of the particle swarm algorithm in search of the insufficiency in the experiment,and put forward the adaptive inertia weight parameters adjustment and chaos optimization strategy,and contrast chose in small populations could keep good search performance of Tent mapping model,finally through the experiment,the improved algorithm can increase the search speed by 1.5 times,The success rate increased by 10%,with better search performance and stability.