Research On Integrated Polarization-handling Devices Based On Silicon Nano-waveguides

With the rapid development of information technology,people have higher requirements for communication broadband and the intelligence of information systems.Photonic integration circuits(PICs)are playing an increasingly important role in areas such as optical interconnection and intelligent sensing.Silicon photonics have become one of the most promising platforms in PIC because of complementary metal oxide semiconductor(CMOS)compatibility,high component density,reduced power consumption.However,there are still some obstacles that limit the expansion of silicon nanowaveguides and devices to more applications and the polarizationinvolved problems are included.The main work of this paper is to use silicon nanowaveguides and silicon hybrid surface plasma waveguides to fabricate various polarization-handle devices to address the polarizationinvolved issues in silicon photonics.This thesis uses optical simulation and nano fabrication to carry out a series of research work on the designed devices.The main research work of the paper are as follows:1.This thesis introduces the importance of silicon-on-insulator(SOI)waveguides to improve the integration of optical paths,and focuses on the polarization of silicon nano-waveguides.The wave optics theory is used to analyze the waveguide transmission characteristics with slab waveguides and strip waveguides as entry points.Common numerical calculation methods(finite element method and finite difference time domain method)and boundary conditions(perfectly matched layers)are introduced.The experimental production process and test platform are introduced.2.This thesis introduces the subwavelength grating waveguide and its mode characteristic.First,a TM-pass polarizer based on subwavelength structures is proposed.Our simulation results show an extinction ratio of more than 30 d B,and an insertion loss of less than 1 d B in a working bandwidth of 335 nm.Moreover,the thesis numerically and experimentally demonstrates a polarization beam splitter based on subwavelength structures.The coupling length is only ? 7.2 ?m.For the fabricated device,high extinction ratio >10 d B and low insertion loss <2.5 d B can be achieved in the wavelength range of 1460 nm-1610 nm.3.This thesis analyzes the polarization characteristics of silicon hybrid surface plasmon nanowaveguides,including the effects of waveguide size,structure,and wavelength on their mode field distribution and refractive index,and compares them with silicon dielectric waveguides and silicon surface plasmon waveguides.Then,a polarization splitter and rotator based on bent directional coupling is designed and researched.The present device features ultra-compact size and broadband operation.Our simulation results show an extinction ratio greater than 23 d B and an insertion loss lower than 0.8 d B at the central wavelength of 1550 nm.The TM-to-TE polarization conversion efficiency is better than 95% and an extinction ratio is greater than 17 dB over a bandwidth of 80 nm.