Design Of Silicon Waveguide Demultiplexers Based On Digital Metamaterials

Demultiplexers integrated in silicon-based waveguides can separate and direct different incident light to different output ports according to their physical characteristics such as polarization,mode,and wavelength,which can improve the effectiveness of information transmission in physical waveguides and increase the transmission capacity of optical fiber communication systems.At the same time,the polarizer can be an important component of polarization-related devices to realize the transmission control of TEO and TMO polarization modes in polarization demultiplexers.To further meet the high requirements of photonic integrated devices,scientific research on photonic devices began to introduce intelligent optimization algorithms to design waveguide structures in a digital coding-like manner to obtain silicon waveguide devices based on digital metamaterials.In silicon waveguide devices,square pixel units whose dielectric is silicon and air are combined in a 0/1 binary-like arrangement to form the final desired digital metamaterial.With a known target function to be achieved by the waveguide device,the silicon waveguide defines the target function of the device and optimizes the digital metamaterial by means of inverse design,resulting in a silicon waveguide device with the target function.Such an intelligent optimization means to design digital metamaterials breaks through the design ideas limited by existing physical theories and explores to tap new physical mechanisms to make silicon-based waveguide demultiplexed devices with high dimensionality,high transmission capacity,small footprint,low loss,and high CMOS compatibility.In this paper,the design study revolves around silicon-based waveguide demultiplexers,as follows.In this paper,we combine the finite element method with the density method(DM)and the method of moving asymptote(MMA)to describe the distribution of silicon and air in the functional region,respectively,and find the optimal solution for the topology optimization design of ultracompact digital metamaterials in two and quasi-three dimensions to obtain a series of silicon waveguide devices with target functions.In this paper,four demultiplexers in three dimensions of polarization,mode,and wavelength are designed,and waveguide polarizers are designed for better controlled transmission of polarization in polarization demultiplexers.Ultimately,this paper simulates a 3D model waveguide devices based on 3D finite difference time domain(FDTD)simulation of silicon on insulator(SOI),which includes TEO/TMO polarization demultiplexer,TE0/TE1 mode demultiplexer,1550nm/1310nm wavelength demultiplexer and 1500nm/1600nm wavelength demultiplexer.The digital metamaterial size of the four demultiplexers is only 1.55μm×1.55μm.The final 3D FDTD simulation results demonstrate comparable and good performance of the device target functions:the transmission efficiency of all four demultiplexers is higher than 44.5%of TEO in the polarization demultiplexer,the contrast is higher than 14.1dB of TE1 in the mode demultiplexer,and the crosstalk is smaller than-15.1dB of TEO in the mode demultiplexer.The crosstalk is less than-15.1dB of TE0 in the mode demultiplexer.