Buried heterostructure complex-coupled distributed feedback 1.55 μm lasers fabricated using dry etching processes and quaternary layer overgrowth

An attractive process for fabricating buried heterostructure complex-coupled distributed feedback (BH-CC-DFB) lasers emitting at 1.55 μm has been developed. It combines low damage chemically assisted ion beam etching (CAIBE) for grating definition, subsequent overgrowth of a quaternary GaInAsP layer (λPL=1.22 μm) by low-pressure metalorganic vapor phase epitaxy, reactive ion etching for mesa definition and semi-insulating InP:Fe regrowth by hydride vapor phase epitaxy. CAIBE improves grating uniformity, GaInAsP layer overgrowth increases gain coupling and semi-insulating regrowth facilitates lateral mode confinement and thermal dissipation. The as-cleaved BH-CC-DFB lasers fabricated with the above combination show a statistical single mode yield of 87% and a very high side-mode suppression ratio up to 55 dB. A −3 dB bandwidth of 10 GHz is also demonstrated.