Silicon-based Integrated Polarization Beam Splitter With Asymmetrical Directional Coupler

In recent decades,the exploitation of advanced modulation formats and multidimensional multiplexing technologies has accelerated the development of optical fiber communication technology greatly.Silicon photonic integration with advantages of high integration?ultra-small size and low power consumption has attracted increasingly attention and has been regarded as the main developing trend of optical communication technology in the field of telecommunication and data communication.However,the significant birefringence due to the high refractive index difference between the waveguide and the substrate in silicon based waveguide devices introduces the polarization sensitive problem which restricts the application range of the silicon based devices.In this paper,we introduce and discuss several solutions to solve this problem,and pay much attention to the polarization diversity scheme.Then silicon based polarization beam splitter?PBS?is investigated,and the mode analysis of the silicon waveguide is carried out.We also discussed the fabrication process and testing methods of silicon based devices.Finally,two kinds of PBS based on bent waveguide are investigated in this paper.The contents and main works of this paper can be summarized as follows.1.The research on PBS which is a key component in the polarization diversity scheme is thoroughly introduced and classified according to operation mechanism.Especially,PBS based on symmetrical directional coupler is summarized and analyzed in detail.2.Several commonly used silicon waveguides are analyzed with FDTD solution,and the fabrication process and test scheme of silicon-based passive devices are also introduced.3.An ultra-compact silicon PBS based on a bridged bent directional coupler?DC?is proposed.The design principle and parameter optimization of the scheme are introduced.We also simulate the transmission characteristics and process tolerance of the device.The polarization extinction ratio of the TE₀ mode and TM₀ mode can reach 23dB and 33dB respectively,besides the PER of the TM₀ mode can remain higher than 20dB within the whole C band.4.A PBS is experimentally demonstrated using a silicon slot waveguide based on bent directional coupler.The polarization extinction ratio?PER?is achieved to 38.3dB and42.4dB for TE mode and TM mode respectively with only 8.4?m coupler length at 1550nm wavelength.The insertion loss for PBS is only 0.92dB and 0.46dB respectively.