Thermo-optic Phase Shifter With Improved FOM Based On Ⅳ Group Materials

In recent years,integrated optical circuits have gained more and more interests.It has high integration and high power density,making it attractive for many applications.Currently,the most promising application of the integrated optical circuits is the hardware platform for artificial intelligence computing.Compared with the traditional hardware architecture,integrated optical circuits have the advantage of parallel computing and no additional energy consumption.As important components of current integrated optic architecture,thermo-optic phase shifters affect the speed and energy consumption of artificial intelligence computation.Thermo-optic phase shifters also play a role in the optical phased arrays which lower the cost and make it more compact.New materials represented by graphene provide new ideas for the improvement of thermo-optic phase shifters.Graphene has high in-plane thermal conductivity and anisotropic heat conductivity,which accelerate the heat transfer to the waveguide.The Si-Ge multilayers has ultra-low thermal conductivity which can effectively prevent heat leakage.Owing to these two materials,thermo-optic phase shifters can be faster and more power-efficient.This thesis characterizes the performance of thermo-optic phase shifters implemented on GOS and GeOI platforms.Main works and the novelties of this thesis are listed below.The procedure of numerical modeling is firstly presented.The initial structures of the thermo-optic phase shifters are given on the GOS and GeOI platforms.The characteristics of the thermo-optic phase shifters are numerically simulated by a finite element method.The heat conduction is analyzed for each structure.The structural parameters are scanned and their impact is studied.Thermo-optic phase shifters are further optimized using new materials,the material thickness is also studied.Several methods,including creating air trenches and undercuts,modifying microheaters,are used to optimize the structure of GOS thermo-optic phase shifter and the FOM is improved to 342.25 m W·μs.The FOM achieves 336.63 m W·μs after few-layer graphene is added under the waveguide.For GeOI thermo-optic phase shifters,the FOM is improved to 49.99 m W·μs by creating air trenches and changing the heating method.After adding few-layer graphene under the waveguide,the FOMs of thermo-optical phase shifters is optimized to 35.15 m W·μs.Finally,Si-Ge multilayers are added under and above the waveguide and micro-heater and the FOM achieves 10.54 mW.