Performance enhancement of distributed feedback laser with a partial grating

Distributed feedback (DFB) lasers that are widely used in high-speed communication nowadays usually use end-facet coating in order to seek a balance between fabrication difficulty and device performance. This paper investigates DFB lasers with a partial grating structure that is immune to the phase uncertainties at the end-facet with high-reflection (HR) film and the improvement of its output chirp characteristics. It is found that, after parameter optimization, the carrier concentration and photon density distribution along the partial grating DFB(PG-DFB) laser cavity can be more uniform, which helps to obtain a better production yield. In addition, a compromised choice of the length of grating region and non-grating region can ensure stable single-mode output, as well as sub-10 mA threshold and high slope efficiency (SE). We also find that the PG-DFB laser can reduce the transient chirp by about 5 GHz compared to conventional DFB laser with uniform grating.