Mechanism for high singlemode stability of gain-coupled DFB laserswith periodically etched quantum wells

The sidemode suppression ratio of gain-coupled DFB lasers with periodically etched quantum wells is analysed by a more accurate model for amplified spontaneous emission. It is shown that the periodic etching of quantum wells is very effective for providing a high side-mode suppression. The mechanism for the high singlemode stability is explained by the effective modal gain. which has an enhancement at the longer wavelength side of the Bragg stopband