Optically pumped GaInN/GaN-DFB lasers: overgrown lasers and vertical modes

The laser operation of GaInN/GaN distributed feedback lasers (DFB) with separate confinement double hetero or multi quantum well structures on SiC is demonstrated. The separate confinement heterostructures were realized by overgrowing the dry etched DFB gratings. Optically excited lasing is observed with emission wavelengths between 402 and 421 nm, depending linearly on the grating period. The laser thresholds are compared to laser thresholds of non overgrown DFB lasers. Furthermore, the wavelengths selectivity of DFB lasers is used to study vertical modes in laser structures grown on sapphire. In a thick asymmetric laser structure, higher vertical modes can be distinguished because of their different effective refractive index ηeff. In thin heterostructures, the vertical ground mode is lasing.