Watt-level, high wall plug efficiency, continuous-wave room temperature quantum cascade laser emitting at 7.7µm.

In this article, a InP based strain-balanced InGaAs/InAlAs quantum cascade laser emitting at 7.7µm is reported. The active region is based on a slightly-diagonal bound to continuum design with 50 cascade stages and a low voltage defect Δ of 96 meV. By optimizing the active region and waveguide structure, the waveguide loss α of 1.18cm are obtained, which contribute to a high wall-plug efficiency (WPE) of 9.08% and low threshold current of only 1.09 kA/cm in continuous-wave(CW) operation at 293K. The maximum single facet output power of 1.17W in CW operation and 2.3W in pulsed operation are measured at 293K. The narrow ridge and buried ridge structure epi-side-down-mounted on the diamond heatsink improved the heat dissipation of the device. A beam of pure zero order mode and a broad external-cavity tuning range from 7.16µm to 8.16µm are also achieved.