LAUSR

For external cavity semiconductor lasers (ECSLs), high coupling efficiency is critical to reducing the linewidth. In this paper, the coupling efficiency between the laser diode and the waveguide grating has been improved, with proposals for its improvement presented, including adding spot-size conversion (SSC) and using a silicon-on-insulator (SOI) waveguide. The results indicate an increase of coupling efficiency from 41.5% to 93.1%, which exhibits an improvement of approximately 51.6% over conventional schemes. The relationship between coupling efficiency and SOI waveguide structures is mainly concerned in this article. These findings provide a new way for the future research of the narrow linewidth of ECSL.