Proposed enhancement of side-mode suppression ratio in /spl lambda//4 shifted distributed feedback lasers with nonuniform diffused quantum wells

An enhancement of the side mode suppression ratio, by utilizing interdiffused quantum wells, of a /spl lambda//4 shifted distributed feedback laser is demonstrated theoretically. It is found that by introducing a diffusion step along the longitudinal direction of the quantum-well active region, the suppression ratio can be improved significantly for large /spl kappa/L (>2.6) devices. The maximum power for single longitudinal mode operation is increased by more than 50 mW.