Research On Silicon-based Vertical Coupler Based On Subwavelength Grating

With the development of information technology,communication,computation,sensor,artificial intelligence and even consumption put forward higher requirements for information processing and transmission speed.Compared with electron,photon,as the carrier of information processing and transmission,has more stable and controllable modulation and multiplexing dimensions,such as amplitude,phase,wavelength,polarization state,mode,etc.,with greater bandwidth and higher spectrum utilization rate and larger communication capacity become the important direction of the development of next generation information technology.In particular,silicon-based optoelectronic technology,which uses the working principle of micro/nano optoelectronic devices,and uses technologies and methods compatible with silicon-based integrated circuit technology to integrate different devices on the same silicon substrate,has the advantages of high integration density,large transmission capacity,low power consumption,large-scale standardized production and so on,and is favored and developed rapidly.At present,the 90 nm process line of silicon-based photonics has gradually matured,and the increasing process level provides more design space for more new structures and new functions of silicon-based optoelectronic devices.At present,with the support of technology,the silicon-based subwavelength grating waveguide is used to replace the silicon-based optical waveguide.By adjusting the duty cycle to adjust the equivalent refractive index of the waveguide,the dimension of operation is expanded in the aspects of phase control,polarization control,optical field coupling,etc.,and a series of new devices based on the subwavelength grating are produced.In this paper,the mode analysis method and Finite-Difference Time-Domain method are used to establish the analysis model of subwavelength grating and related devices,and the simulation design is carried out.The coupling process of subwavelength grating is analyzed by using the coupling mode principle,and the basic characteristics,working mechanism and coupling process of subwavelength grating are clarified.On this basis,this paper also applies directional coupling to vertical coupling,designs a kind of silicon-based straight waveguide vertical directional coupler and a kind of subwavelength grating vertical directional coupler,analyzes and summarizes the structural parameters and working characteristics of the two vertical directional couplers.In order to meet the requirements of silicon-based 3D heterogeneous integration for vertical couplers,a novel silicon-based vertical taper coupler based on subwavelength grating is designed.By establishing the coupled mode analysis and equivalent index model of subwavelength grating,the basic structure of a new silicon-based vertical coupler for Si-LiNbO3 heterogeneous integration is proposed.Through numerical simulation,the device parameters are further optimized.Combined with the requirements of 90 nm silicon optical technology,a silicon-based vertical coupler with a length of only 15 ?m is optimized.The size of the device is only one tenth of that of the traditional adiabatic tapered vertical coupler.At the same time,it has a large fabrication tolerance,and has a good application prospect in the field of silicon-based 3D heterogeneous optoelectronic integration.