Broad gain bandwidth injectorless quantum-cascade lasers with a step well design

The authors present a broad gain bandwidth injectorless quantum-cascade laser (QCL) with a "short period superlattice" design which provides an equivalent GaInAlAs alloy quantum step well in each active module. Devices employing the proposed step well design demonstrate an ultrabroadband gain spectrum of 480 cm-1 (∼4 μm) around the threshold at room temperature in pulsed mode. The fabricated 30 μm wide and 4 mm long laser shows the lowest room temperature threshold current density of 1.1 kA/ cm² among the broad gain QCLs emitting at similar wavelengths and a high slope efficiency of 1.6 W/A at room temperature in pulsed mode.