Emission spectra and mode structure of InAs/GaAs self-organized quantum dot lasers

A study of the emission spectra and mode structure of InAs/GaAs self-organized quantum dot lasers is presented. In contrast to conventional bulk or quantum well lasers, the number of lasing modes increases above threshold. This behavior is shown to be consistent with carriers localized in noninteracting dots and a resultant inhomogeneously broadened gain spectrum. The lasing spectra are found to have a complicated form with groups of longitudinal modes separated by nonlasing spectral regions and lasing occurring via a number of different lateral modes. These characteristics are discussed in terms of the spatially discrete nature of the quantum dots.