Multi-spectral lasing characteristics of InAs/GaAs quantum dot laser

•Multi-spectral lasing of InAs/GaAs QD laser is observed.•The multispectra are not caused by the cavity size and the supper radiance.•The physics origin is discussed by the non-uniform size distributions of QD.

The emission wavelength and mode structure of InAs/GaAs quantum dot (QD) lasers are reported. The active region consists of five-stacked QD layers with each QD layer formed by varying thickness of InAs gown by gas source molecular beam epitaxy. At operation temperature of 20 °C, the ridge waveguide laser emits more than 33 mW optical power from one of the cleaved facets under continuous-wave mode and broad gain spectra are obtained due to a large size distribution of InAs QDs. The lasing spectra are found to be a series of complicated longitudinal modes separated by non-lasing spectral regions. We proved experimentally that those behaviors are not relative to the cavity dimension or the supper radiance modulated by photon reflecting in vertical facets. The lasing characteristics can be explained in terms of spatially discrete nature from the non-uniformity size distribution of quantum dots.