Polarization Insensitive Edge Coupler Assisted by Subwavelength Grating and Suspended Structure
Yaqian Li, Min Wang, Sipan Yang, Xueling Quan, Jinbin Xu, Liying Wu, Min Liu, Xiulan Cheng
Abstract
Based on the Si-Si3N4 hybrid photonic platform, an integrated edge coupler embedded with both sub-wavelength grating (SWG) waveguide and suspended structure was demonstrated. The proposed device structure and geometrical parameters were fully optimized to realize efficient optical interconnections with standard single-mode fiber (SMF-28). The coupling loss of 0.86 dB/port for TE mode and 0.94 dB/port for TM mode was achieved with a remarkable polarization dependent loss (PDL) less than 0.1 dB at the input wavelength of 1600 nm. It revealed that the integrated edge coupler assisted by sub-wavelength grating can further reduce the PDL. Moreover, the device also exhibited the advantages of large alignment tolerance. The alignment tolerances for 1-dB excess loss are ±1.8 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pm 2.5~\mu \text{m}$ </tex-math></inline-formula> in horizontal and vertical direction, respectively.