A Semi-constraint Method For Optimized Design Of Passive Device Based On Multilayer Optical Waveguide

The rapid development of optical communication and optical network demands photonic integrated chip(PIC)with smaller footprint,denser integration and more advanced function.Taking advantage of three-dimensional integration,multilayer waveguide gives answer to this issue.The process difficulty of multilayer waveguide desires automated optimized design to achieve complex multilayer PIC.A semi-constraint optimized design method for passive waveguide device is proposed in this thesis.Taking a two-layer Silica-on-Silicon(SoS)waveguide for example,the proposed method is applied to passive waveguide device and verified experimentally.Firstly,the objective function and the conversion degree are defined to evaluate the device performance and geometry complexity,respectively.The optimized design process is reduced to minimize the objective function with constraint of conversion degree.The semi-constraint optimized design method for passive waveguide device is proposed with one-dimensional and two-dimensional models.Secondly,the waveguide passive device based on two-layer SoS waveguide is chosen to verify the proposed method.The transmission mode of two-layer SoS waveguide is analyzed utilizing finite element method.The single mode transmission condition is obtained at 1310 nm and 1550 nm.The influence of waveguide size,layer space and relative offset on the transmission mode is analyzed to obtain the waveguide structure parameters.Thirdly,the proposed method is applied to optimized design of passive device based on two-layer SoS waveguide.A multi-mode waveguide 3 dB coupler and a wavelength demultiplexer are designed based on one-dimensional and two-dimensional models of the proposed method,respectively.The optimal device structure and parameters are obtained.The performance of the device is given according to simulation.Furthermore,the fabrication tolerance of the device is analyzed.Finally,the wavelength demultiplexer obtained with the proposed method is fabricated based on two-layer SoS waveguide.The measurement and coupling system is constructed to test the fabricated wavelength demultiplexer chip.The experimental result basically conforms to theoretical design except the extinction ratio and polarization dependent loss,which results from the nonuniform pressure in top layer waveguide.