High-efficiency coupling between silicon waveguides and single-mode fibers by 3D taper edge couplers

The present study addresses the challenge of limited coupling efficiency between silicon optical waveguides with small cross-sectional dimensions and single-mode fibers in current silicon photonics integrated chips. To enhance the coupling efficiency with single-mode fibers, the investigation employs a 3D taper structure SSC(Spot Size Converter). This paper presents the design of a 3D taper structure SSC end-face coupler with a linearly varying width, height, and length, with the objective of matching the dimensions of the silicon optical waveguide, which are 0.45*0.22μm. The width and height of the SSC exhibit a range of variation between 0 and 20 micrometers, while the length is adjusted within a range of 0 to 200μm. A software simulation was conducted using the FDTD(Finite-Difference Time-Domain) algorithm to investigate the coupling between single-mode fibers and the SSC at wavelengths of 1310nm and 1550nm. The objective was to achieve efficient coupling between single-mode fibers and silicon optical waveguides. The coupling efficiency maps corresponding to the aforementioned dimensions have been obtained, and the range of permissible dimensions for the silicon optical waveguide SSC has been determined. Subsequently, specific coupling efficiencies were simulated for corresponding wavelengths. The analysis demonstrates that the 3D taper structure SSC end-face coupler, which exhibits simultaneous changes in width and height, attains coupling efficiencies exceeding 80% for both 1310nm and 1550nm wavelengths. This result significantly surpasses the traditional silicon waveguide-coupling efficiency, which reaches a maximum of 80%. The 3D Taper structure SSC is demonstrated to possess distinct advantages in this study. The 3D Taper structure SSC end-face coupler, as discussed in this paper, enables coupling efficiencies above 89.2%(enhancing the coupling efficiency by approximately 10%) between silicon optical waveguides and single-mode fibers. This represents a significant improvement over traditional end-face coupling efficiencies, which range from 50% to 80%. Furthermore, it enables efficient coupling at both commonly used optical communication wavelengths, namely 1310nm and 1550nm.