High performance and compact polarization beam splitter based on silicon-on-insulator subwavelength grating coupler

A high coupling efficiency silicon grating which serves both as a high extinction ratio polarization beam splitter and a vertical coupler for silicon photonic circuits at the wavelength of 1550nm is presented. The design is based on the Bragg diffraction condition and the phase matching equation by using the rigorous coupled wave analysis (RCWA). For TE-polarized light, the computing coupling efficiency is as high as 69%, and the extinction ratio can reach - 20dB. The efficiency of TM-polarized wave is better than 53% and the extinction ratio is approximately -11dB. The device has compact structure, high TE to TM extinction ratio, low excess loss and wide operation bandwidth. Moreover, the simple fabrication method involves only single etch step and good compatibility with complementary metal oxide semiconductor (CMOS) technology.