Research On Modeling Methods For Compact Models Of Optoelectronic Integrated Devices Based On Complex Mode Matching Method

With the development of silicon-based optoelectronic integration technology,the focus of design has shifted from single devices design to system.Compact models of devices play an increasingly important role as a bridge between the physical characteristics of devices and process of integration.Compact models are used to characterize the performance of devices and can be applied to systems composed of devices to facilitate system simulation.However,compared with the rapid development of integrated optoelectronic devices,the research of accurate compact models which are easy to embed in simulation software is relatively slow.The simulation of optical devices is mainly achieved by solving Maxwell’s equations numerically in time domain or frequency domain.Among them,finite-difference time-domain(FDTD)method,finite-element method(FEM),beam propagation method(BPM)and the mode analysis method have been widely used in academia and implemented in commercial simulation software tools.The first three algorithms are general-purpose electromagnetic field simulation algorithms,which require long simulation times and high computer memory requirements,thus limiting their application in the simulation analysis of large-scale optoelectronic integrated devices and systems.The mode analysis method which has the advantages of clear physical model,low memory requirement and high computational efficiency is a widely used simulation algorithm in optoelectronic integrated devices and systems.However,the simulation accuracy of existing mode analysis algorithms is low,so further research is needed.In view of the above problems,this thesis mainly proposes modeling methods for compact models of optoelectronic integrated devices based on the complex mode matching method,which can improve the efficiency and accuracy of simulation.At the same time,this method can not only be used for rapid simulation of devices,but also can be applied to the circuit simulation to improve the simulation accuracy of optoelectronic integrated system.The main work and innovation of this thesis are as follows:(1)This thesis verifies the modeling method of devices under the rectangular coordinate system based on complex mode matching method.Firstly,the eigenmode equations under the rectangular coordinate system are derived.Then the diffraction problems,interference problems and scattering problems of electromagnetic fields are studied.Finally,compact models of grating coupler(GC),multi-mode interference(MMI)coupler and tapered waveguide converter are established,and the simulation results are compared with FDTD,which proves that the new modeling method proposed in this thesis is consistent with the FDTD algorithm in terms of accuracy,but has smaller computer memory requirements and higher computing efficiency.(2)This thesis proposes a modeling method of devices in cylindrical coordinate system based on complex mode matching method,and takes the focusing grating coupler as an example to establish an efficient compact model.The focusing grating coupler can be divided into two parts:the cylindrical coordinate slab waveguide and the rectangular coordinate slab waveguide.Using the cylindrical slab modes and the twodimensional complex mode matching method,we can obtain the efficient compact model for the focusing grating coupler.Firstly,the eigenmode equation under the cylindrical coordinate system is derived.The 3D focusing grating coupler model is then simplified to a 2D model using the effective index method.Finally,a new model based on complex mode matching method is used to simulate the focusing grating coupler.At the same time,the simulation results are compared with FDTD to prove the applicability and efficiency of the new modeling method for focusing grating couplers.