Performance enhancement of distributed feedback laser with a partial grating

Abstract

Distributed Feedback (DFB) lasers that are widely used in high-speed communication nowadays usually use end-facet strategy 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 waveguide 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 a uniform grating.