High-Efficiency and Compact Polarization-Insensitive Multi-Segment Linear Silicon Nitride Edge Coupler

Edge couplers are widely utilized in photonic integrated circuits and are vital for ensuring efficient chip-to-fiber coupling. In this paper, we present a high-efficiency and compact polarization-insensitive multi-segment linear silicon nitride edge coupler for coupling to high numerical aperture fibers. By optimizing the thickness of the up cladding and introducing air slots in the transverse direction, we have further modified the limiting effect of the mode field. This innovative edge coupler scheme boasts a compact structure and is compatible with existing mature standard processes, with a total length of only 38 mu m. We numerically demonstrate that the proposed edge coupler exhibits a low coupling loss of 0.22 dB/0.31 dB for TE/TM modes at lambda = 1550 nm. Furthermore, the proposed coupler displays high wavelength insensitivity within the range of 1400-1850 nm and maintains a coupling loss of less than 0.2 dB with a manufacturing deviation of +/- 20 nm.