Research On Silicon-based On-chip Active Polarizer And Polarization Beam Splitter With Novel Nano-waveguide

With the rapid development of information science,the demands for the faster speed of information transmission and the higher performance of electronic products.Silicon-based integrated devices have achieved rapid development in the frontier fields such as optical interconnects and smart sensing due to their small size,high integration and the ability to be compatible with highly mature CMOS technology,attracting tremendous attention from both the industries and academics.However,the polarization-sensitive issues in silicon waveguides have been hindering the development of applications.Here the thesis bases on novel nano-waveguide and generalized the coupled mode theory(CMT)to theoretically and experimentally realize two novel polarization control devices.The thesis focuses on polarization-sensitive issues in silicon waveguides,and based on optical simulation and nano-fabrication,a series of research work has been carried out on the design of polarization control devices.The main content of this thesis presents as follows:1.The thesis introduces SOI silicon-based nanowaveguides and their importance for improving integration.,then explains the polarization problem in silicon nanophotonic integration.The transmission principle of the light field in the waveguide is introduced in detail,and the coupled mode theory of the waveguide transmission is analyzed.Besides,several practical numerical simulation methods for calculating the waveguide section mode field and the transmission of propagation light is mentioned,and how to set the boundary conditions in our simulation.2.Based on the chalcogenide phase change material Ge2Sb2Te5(GST),the thesis proposed an active polarizer.Compared to traditional polarizers,active polarizer can work in multiple states.The tunability of the polarizer relies on the considerable change of the optical properties of the chalcogenide phase change material between the amorphous and crystalline phases.The active polarizer consists of an active TE pass polarizer and an active TM pass polarizer.The active TE-pass polarizer has an ultra-high insertion loss of above 28 d B and an ultra-low insertion loss of as little as 0.12 d B.For the TM-pass active polarizer,the extinction ratio in the crystalline state is 25 d B while the insertion loss is only about 0.8 d B.In addition,the measured results of the fabricated active TE pass polarizer are generally able to verify the simulation results.3.Based on silicon-based sub-wavelength grating structure,the thesis numerically and experimentally demonstrates a polarization beam splitter.An ultra-compact footprint of 1.235 ?m×7.2 ?m is achieved.In terms of performance,the device has a wide operating band.The device has an insertion loss of less than 1 d B for both TE and TM polarizations,and a high extinction ratio of greater than 20 d B(19 d B)for TM(TE)polarization,respectively.In addition,the fabrication process of the polarization beam splitter is simple,and experimentally proved that the device has a large fabrication tolerance.The novel polarization control devices proposed in the thesis have positive significance for solving the polarization problem of silicon waveguide,and promotes the further development of silicon photonics.