Polarization Insensitive Edge Coupler Assisted by Subwavelength Grating and Suspended Structure

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.