Self-Formed InGaAs Quantum Dot Lasers with Multi-Stacked Dot Layer

Systematic investigation of lasing characteristics of self-formed InGaAs quantum dot lasers with multi-stacked dot layer is reported. We show that the lasing wavelength is strongly dependent on the number of quantum dot layers and the cavity length. Discontinuous shifts of the lasing wavelength from a high-order subband to a lower-order subband are clearly observed with increasing number of quantum dot layers and with decreasing cavity loss. The possibility of lasing at the ground state of quantum dots is also quantitatively discussed.