Research on 1×4 polarization-independent beam splitter based on silicon waveguide

Abstract

This paper presents a 1×4 polarization-independent beam splitter based on silicon waveguides. The device is mainly consisted of a coupling structure and a sub-wavelength structure. According to the coupled mode theory, in the traditional directional coupled structure, the coupling strength of TM mode is stronger than that of TE mode, which makes it difficult to realize polarization-independent beam splitting. Adding a sub-wavelength structure in the coupling region can weaken the coupling strength of the TM mode while enhancing the coupling strength of the TE mode, so that the coupling strengths of the TE mode and the TM mode are equal. Therefore, polarization-independent beam splitting can be achieved by adjusting the parameters of the directional coupling structure and the sub-wavelength structure. The time-domain finite difference method (FDTD) is used for simulation analysis. The simulation results show that the device can realize polarization-independent beam splitting at 1550nm, the insertion losses of TE and TM modes are 0.36 dB and 0.55 dB, respectively. The length of the device is 23.421 μm and the bandwidth is about 10 nm. The device has the advantages of small size and simple structure, and it is easily to be integrated.