Dynamic Control Of Optical Transmission Based On Silicon Photonic Waveguides

Beam steering technology can achieve target acquisition and aiming,which has been widely applied in optical communication,lidar,medicine and other fields.In recent years,the lens-assisted beam steering has attracted much attention due to its low power consumption and high integration.In this paper,we study two key devices:a waveguide grating structure and a silicon photonic switch.Firstly,a thermally tunable grating structure based on a transparent graphene nanoheater is proposed,which could be used as a grating coupler or a surface emitter.In this design,a single-layer graphene strip is directly spreaded on the grating region,then the grating is heated by the graphene nanoheater.The central wavelength or the diffraction angle is adjusted due to the thermo-optic effect of silicon.The simulation results show that this structure can achieve a center wavelength shift of 30 nm as a thermo-optic grating coupler,and the tunning efficiency is about 0.35 nm/mW;it can achieve a diffraction angle shift of 4.2 ° as a thermo-optic surface emitter,and the tunning efficiency is about 0.05 °/mW.Secondly,a novel 2×2 silicon photonic MEMS switch is designed and fabricated,which combines the total internal reflection principle and MEMS technology to integrate the optical,electrical and micro-mechanical structures.The main structure is a MMI waveguide crossing with a switchable gap.The two sides of the gap are charged to generate electrostatic force which makes the waveguides deform.The gap width is adjusted through changing the voltage to switch the ON and OFF states.Theoretically,in the wavelength range of 1250-1650 nm,the average excess losses are 0.21 dB(OFF),0.18 dB(ON);and the average crosstalkes are-23.57 dB(OFF),-52.12 dB(ON);the average extinction ratioes of the Cross and Bar ports are 23.38 dB(Cross),58.06 dB(Bar);the activation voltage of the ON state is about 45 V.Finally,a silicon photonic MEMS switch based on an electrostatic comb actuator is designed and fabricated,which separates the optical structures from the MEMS structures.The electrostatic comb actuator can adjust the gap width to switch the states.When the initial gap width is 500 nm,in the OFF state,the average excess loss is about 0.18 dB,and the average crosstalk is about-44.49 dB;the average extinction ratio is 44.49 dB(Cross),58.09 dB(Bar),and the driving voltage is about 13.6 V in the ON state.