Research On Polarization Beam Splitting-rotation-multiplexing Integrated Device Based On Thick Silicon Waveguide

With the development of information and communication industry,fiber optical communication systems are widely used,and the increasing demand for signal processing rate and communication capacity has led to higher and higher integration of optical circuits.In recent years,silicon on insulator（SOI）platforms have received high attention in the field of photonic integration due to their good compatibility with complementary metal oxide semiconductor（CMOS）processes,but the presence of high refractive index differences between their waveguides and cladding layers introduces significant polarization-related losses and polarization mode dispersion,limiting the application of silicon-based optoelectronic devices.Polarization diversity systems have been proposed to solve this problem,and polarization control devices,as the core of this system,are of great research importance.In this paper,three polarization control devices based on thick silicon-based waveguides are proposed,namely,a polarization beam splitter（PBS）based on a three-waveguide asymmetric directional coupler（ADC）,which achieves the function of separating TE and TM modes in arbitrary incident light and outputting them from different channels by reasonably designing the waveguide width so that the TM₀ mode meets the phase matching condition and cross-coupling occurs with the help of TM₁ mode,and the TE₀ mode is phase-mismatched without cross-coupling;a polarization rotator（PR）based on the tangent waveguide,through the asymmetric cross-section design,uses the mode mixing principle to realize the polarization rotation and replaces the corner area of the tangent waveguide with a subwavelength grating（SWG）,realizing the function of rotating the incident TM mode input to TE mode output in the broadband;a polarization beam splitting-rotation-combining integrated device,cascading the above two devices with a combiner and a filter,which realizes the function of converting arbitrary incident light into TE mode and output from a single channel.The simulation results show that the designed integrated device has a polarization extinction ratio of 45d B and insertion loss of 0.53 d B at the center wavelength of 1550 nm,and a polarization extinction ratio of more than 30 d B and insertion loss of less than 1 d B in the wavelength range of 1500nm-1575 nm,with a device size of 56μm.The designed polarization beam splitting-rotation-combining integrated device has good performance and compact structure,which can be applied to high speed and large capacity optical communication system and have important application value to improve the performance and integration of optical communication system.