Research Of Multimode Interference Optical Isolator On Silicon Substrate

With the rapid and continuous development of information technology,Internet and IOT show more and more influence on people's daily life.This trend increases the demand for faster and better communication network.Optical fiber communication system with high speed and high capacity has been widely studied.With the development of silicon photonics in recent years,the integration of all kinds of optical devices on a silicon chip has been verified by theory and experiment.To achieve full functionality of a silicon photonic chip,it is necessary to fabricate an integrated photonic device in front of the laser,to avoid light reflection,intensity and frequency noises and protect the laser from damage.The devices we study show characteristics of forward passing and backward cut-off,which is called an optical isolator.Compared with the descrete single crystal optical isolator,magnetio-optical waveguide optical isolators on silicon show characteristics of nonreciprocity and low cost,small volume,low loss,high mechanical stability and other advantages,making themselves worth research.In this paper,we study a multimode interferometer(MMI)type optical isolator on silicon substrates detailedly.Firstly,the nonreciprocal phase shift effect(NRPS)is related to the mode profile in magneto-optical waveguides.By solving the Maxwell Equations,we calculated the mode profile and NRPS of the waveguide device.We use finite element(FEM)for solving mode of the waveguide,and put forward a design of with a large NRPS difference of multimode interference waveguide by the theory of nonreciprocal phase shift,the waveguide is small and easy to fabrication.As for the simulation of isolator performance,the excitation efficiency of each mode is calculated by the coupled mode theory,and then the final performance parameters of the MMI optical isolator are calculated by the multimode interference theory.In the end,we upgraded and improved the whole design,and put forward the design of broadband and multimode interference(MMI)magneto optic isolator based on TE mode.This paper presents a multimode longitudinal multimode waveguide interferometer(MMI)design of optical isolator,which makes the nonreciprocal phase shift get greatly improved,reduce device length to 1/10 of the original one.Then analyzes the characteristics of dispersion curves and makes the device with broadband.In the aspect of broadband,the factors that affect the isolation bandwidth of the device are analyzed qualitatively,which shows guiding significance for the design of multimode interference devices.Finally yet importantly,the influence of the process parameters on the performance of the device is analyzed.