Two-state lasing in a quantum dot racetrack microlaser.

The peculiarities of two-state lasing in a racetrack microlaser with an InAs/GaAs quantum dot active region are investigated by measuring the electroluminescence spectra at various injection currents and temperatures. Unlike edge-emitting and microdisk lasers, where two-state lasing involves the ground and first excited-state optical transitions of quantum dots, in racetrack microlasers, we observe lasing through the ground and second excited states. As a result, the spectral separation between lasing bands is doubled to more than 150 nm. A temperature dependence of threshold currents for lasing via ground and second excited states of quantum dots was also obtained.