Very low threshold current density GSMBE 1.55 µmgain-coupled DFB lasers

1.55 µm gain-coupled DFB lasers with a periodically etched active layer have been realised using dry-etching and gas source molecular beam epitaxy. Threshold current densities as low as 700 A/cm2 have been achieved which is an improvement on previous values reported for gain gratings. Optimised active layer etching and cleaning technologies are reported.