Optical Design of Distributed Feedback Lasers-on-Thin-Film-Silicon

We design and theoretically evaluate the performance of a novel distributed feedback (DFB) laser-on-thin-film-silicon through its coupling coefficient, threshold current, and slope efficiency. In the DFB laser-on-thin-film-silicon, the optical mode is confined and guided by the narrow III-V-based epi-layers, resulting in an optical field confinement of ~15%. Hence, through the variation of the width of the epi-layers, the optical mode-overlap with the gratings etched on the silicon could be changed. This changes the coupling coefficient of the DFB laser, providing a superior flexibility in reducing the threshold current and increasing the slope efficiency of the laser by ~3× to 4×, in comparison with the previous work on DFB laser-on-silicon.