Room-temperature operation of electrically pumped quantum-cascade microcylinder lasers

We present the lasing properties of microcylinder lasers that were processed into a quantum-cascade heterostructure. At room temperature, the $\mathrm{GaAs}/{\mathrm{Al}}_{\text{0.45}}{\mathrm{Ga}}_{\text{0.55}}\mathrm{As}$ superlattice structure lases at 12.55 μm. Low mirror losses, an inherent advantage of microcylinder lasers, result in a low threshold current density of 2.2 kA/cm² at 78 K. The microcylinder lasers compare favorably to both Fabry–Pérot and distributed feedback cavities that were processed from the same material. The maximum operating temperature of the microcylinders, 54 °C, exceeds the previously reported maximum operating temperature, −3 °C, for an InP-based microlaser.