Basic Research On Silicon-Based Polarization-Independent Electro-Optic Modulator

The optical modulator is used to dynamically regulate the output optical signal by applied electrical signal,therefore occupying an important position in high-speed and long-distance optical fiber communication systems.In recent years,the optical interconnection technology on the silicon substrate has become an important development direction of the modulator.Therefore,how to obtain higher performance electro-optic modulators has become a research hotspot in the field of integrated optoelectronics and application markets.In order to obtain high-speed,high-bandwidth,and low-loss modulators,some typical electro-optical materials such as lithium niobate,organic polymers,graphene,etc.have been proposed.Although optical modulators have a great development in recent years,most of them still have to face the problem of polarization sensitivity,which means that if the optical signal whose polarization direction changes in the fiber enters the polarization-sensitive modulator,it will inevitable cause polarization-dependent loss,which will affect the modulation efficiency.Therefore,once the polarization sensitive problem of the modulator can be solved,the modulation efficiency of the device will be greatly improved.Based on the investigation of the current mainstream silicon-based polarizationindependent electro-optic modulators and related work,this paper proposes two methods to realize polarization-independent modulation based on the optical waveguide mode theory,and according to these two methods,three silicon-based polarization-independent electro-optic modulators are proposed,combined with theoretical analysis and simulation work,its feasibility will be verified.The specific research work is as follows:1.Investigating the current research status of electro-optic modulators and polarization-independent electro-optic modulators,focusing on the analysis of the principle for achieving polarization-independent modulation.Put forward my own opinions on how to improve the problem about the process feasibility,complexity,performance disadvantages of various devices that realize polarization-independent modulation.2.Based on waveguide mode theory and waveguide mode conversion theory,two methods to achieve polarization-independent modulation are proposed.The first way is to use the electro-optic material which having different effect of overlapping different polarization components of the light,and the position for the electro-optic material in the waveguide will be reasonable located,which will realize the similar effect to different optical components;the other way is to achieve the mode conversion before the modulation,which means that the mode that interacts weakly with electro-optical materials in the modulation area will be converted to that interacts strongly with electrooptical materials in the modulation area,and through the mode analysis of a typical strip waveguide,the important structural parameters for realizing mode conversion are obtained.3.Based on two methods for realizing polarization-independent modulation,three silicon-based polarization-independent electro-optic modulators are proposed,including two strucures based on mode conversion and a structure of graphene titled in the waveguide.Through a series of simulation work,the structural parameters are optimized and the feasibility of realizing polarization-independent modulation is verified.Compared with the previous work,the advantages and disadvantages for the performance characterization and process are analyzed,and the areas for improvement are also proposed.