Design And Simulation Of Silicon Organic Hybrid Integrated Mach Zehnder Modulator

Microwave photonic link technology is an interdisciplinary frontier subject of microwave technology and photonic technology.It has excellent application prospects in the fields of radar system,broadband access and microwave and photonic signal processing.As one of the more important core components in the system,the electro-optic modulator is mainly used to modulate the electrical signal to the light wave for optical domain transmission and processing.In order to meet the application requirements of highperformance transmission of microwave photonic link and fast processing of microwave photonic signal,electro-optic modulator needs to have large modulation bandwidth and high modulation efficiency.Silicon organic hybrid integration technology combines the characteristics of high electro-optic coefficient polymer materials and CMOS compatible silicon optical processing technology.The electro-optic modulator designed under this technology meets the needs of high performance of microwave photonic link.In this paper,the research work on the design and optimization of silicon organic hybrid integrated Mach Zehnder electro-optic modulator is as follows:Firstly,in order to improve the modulation efficiency of the modulator,the waveguide structure parameters such as slot width,silicon waveguide width and silicon flat layer height are optimized,so that most of the optical power can be concentrated in the slot for transmission as much as possible.The loss under the optimal waveguide structure reaches2.5322 d B/mm.Because the waveguide structure of the modulator adopts the slot waveguide structure,which will produce a large mode mismatch when docking with the straight waveguide structure,a multimode interference(MMI)mode coupling structure is designed and optimized to improve the coupling efficiency when docking with different waveguide structures.The coupling efficiency of the mode coupling structure optimized by simulation reaches 94.32%.Secondly,a uniform grating coupler is designed and optimized,because the traditional silicon-based optical waveguide is usually composed of two materials with no refractive index,while the waveguide structure of our modulator structure adopts slit waveguide,which will bring huge coupling loss.The grating coupler can input and output light at any position of the waveguide,which can carry out optical coupling more flexibly and efficiently,so as to reduce the loss and improve the efficiency.The coupling efficiency of the optimized grating coupler reaches 57.2%.Finally,the electrode region of the modulator is theoretically analyzed and optimized.The theoretical formulas of transmission loss of microstrip electrode and coplanar electrode with different electrode structures,the theoretical derivation of modulation principle and the influence of different electrode structures on modulation bandwidth are compared.The structural parameters such as electrode width and electrode length are optimized.It is concluded that the modulated half-wave voltage of the optimized electro-optic modulator is1.13 V,the half-wave voltage-length product is 0.044V·m,and the bandwidth reaches77 GHz.