Above-threshold analysis of three-section DFB/DBR lasers with second-order gratings

An above-threshold static analysis has been performed on a three-section DFB/DBR laser with a continuous second-order grating. The laser has a center pumped section that is terminated by two unpumped grating sections. The results confirm earlier experimental observation that the laser operates with a peaked nearfield intensity distribution along the laser cavity. The values of the grating parameters and the active-section-to-total-cavity-length ratio associated with this mode of operation are obtained. They indicate good tolerance in these design parameters. The DFB/DBR laser is also found to have reduced longitudinal spatial hole burning and a smaller effective linewidth enhancement factor compared with a uniformly pumped single-section, second-order DFB laser. The introduction of asymmetry in the DFB/DBR laser results in poorer side-mode suppression compared with the symmetric DFB/DBR laser