A High-Efficiency Wideband Grating Coupler Based on Si 3 N 4 and a Silicon-on-Insulator Heterogeneous Integration Platform

• Published in: Materials Vol. 17; no. 4
• Main Authors: Liu, Meng, Zheng, Xu, Zheng, Xuan, Gong, Zisu
• Format: Journal Article
• Language: English
• Published: Switzerland 18-02-2024
• Subjects: coupling efficiency; grating coupler; wideband; FDTD
• ISSN: 1996-1944; 1996-1944

To fully utilize the advantages of Si
N
and Silicon-On-Insulator to achieve a high-efficiency wideband grating coupler, we propose and numerically demonstrate a grating coupler based on Si
N
and a Silicon-On-Insulator heterogeneous integration platform. A two-dimensional model of the coupler was established and a comprehensive finite difference time domain analysis was conducted. Focusing on coupling efficiency as a primary metric, we examined the impact of factors such as grating period, filling factor, etching depth, and the thicknesses of the SiO
upper cladding, Si
N
, silicon waveguide, and SiO
buried oxide layers. The calculations yielded an optimized grating coupler with a coupling efficiency of 81.8% (-0.87 dB) at 1550 nm and a 1-dB bandwidth of 540 nm. The grating can be obtained through a single etching step with a low fabrication complexity. Furthermore, the fabrication tolerances of the grating period and etching depth were studied systematically, and the results indicated a high fabrication tolerance. These findings can offer theoretical and parameter guidance for the design and optimization of high-efficiency and broad-bandwidth grating couplers.