Two-State Lasing in Quantum Well and Quantum Well-Dot Lasers

The switching of lasing from the ground state to the excited state with increasing current in InGaAs/GaAs lasers with quantum well-dots (QWDs) and quantum wells with different waveguide widths has been studied. It was shown that lasers with a waveguide of width 0.45 mu m did not switch to the lasing mode through an excited state at current densities up to 48 kA/cm2 due to peculiarities of the density of states in QWDs, in contrast to lasers with quantum wells. Generation through an excited state in QWD lasers occurred when the waveguide width increased up to 0.78 mu m and was accompanied by switching from the fundamental to the second-order optical mode.