Research On Polarization Multiplexer And Switchable Polarization Beam Splitter Based On Silicon-based Optical Waveguide

With the development of the times,people's demand for data transmission speed and data capacity is increasingly urgent.The emergence of integrated optics solves the problems of small data capacity,large electromagnetic crosstalk,and unstable performance in traditional electrical interconnections.As one important field of the integrated optics,the silicon nano-waveguides has attracted the attention of scientists due to its advantages such as high refractive index difference,high-density integration,compatibility with CMOS technology,and low cost.However,the high refractive index difference also brings a negative effect,that is,the polarization-involved issues in the waveguide.This main work focuses on the polarization-involved issues.Firstly,it is the application of polarization on the silicon substrate.A silicon photonic sensor based on the polarization multiplexer is designed.Then a switchable polarization beam splitter is proposed to solve the polarization problem on the silicon substrate.The work of the thesis also provides more novel ideas for solving polarization-involved issues in silicon-based optical waveguides,and help to open up new ways for the designs and development of silicon-based nano-integrated photonic devices.The main work of the thesis is as follows:(1)The basic theory of silicon-based dielectric waveguides is introduced,and three commonly used numerical calculation methods are introduced: finite element method,finite difference method and finite difference time domain method.Then,a brief introduction to the manufacturing and testing process of silicon-based optical waveguides is given,which provides a certain theoretical basis and guidance for the design and processing of silicon-based photonic devices.The basic theory of silicon-based hybrid surface plasmon waveguide is studied.A novel hybrid plasma waveguide with cylindrical air gap and fully symmetrical metal triangular rib and gain medium triangular rib is designed.Analyze the performance of the waveguide structure.The results indicate that the designed waveguide has strong optical field confinement capability and ultra-low propagation loss.(2)Using polarization beam splitters,a silicon photonic polarization multiplexing(PM)sensor featuring both a large range and a high resolution is proposed and experimentally demonstrated.The sensor includes a Fabry–Pérot(FP)resonator and a microring resonator(MRR)functioning as the sensing parts.With PM technology,the FP resonator only works on the transverse-electric mode while the MRR only on the transverse-magnetic mode.Thus,the proposed sensor can simultaneously achieve a large range with a short FP resonator and a high resolution with a high-Q MRR.Measured results show a range of 113 ? and a resolution of 0.06 ? for temperature sensing,and a range of 0.58 RIU(refractive index unit)with the resolution of 0.002 RIU for analyte refractive index sensing.(3)Based on the symmetrical directional coupler,a novel switchable polarization beam splitter is designed.The function of polarization switchable is introduced into the polarization beam splitter for the first time.The polarization beam splitter is mainly composed of two parts: the coupling straight waveguide and the bending waveguide at the input and output end.The structure is simple and easy to manufacture.The length of the coupling waveguide is designed to meet the conditions of transverse-electric mode and transverse-magnetic mode splitting.The polarization mode of the output end is switched by heating,and the polarization switchable function is realized.The polarization beam splitter has a high extinction ratio and low insertion loss.In addition to being used in polarization multiplexing systems,it can also be widely used in optical routing and optical switching technology.