High performance bi-functional quantum cascade laser and detector

An improved bi-functional quantum cascade laser and detector emitting and detecting around 6.8 μm is demonstrated. The design allows a significantly higher laser performance, showing that bi-functional designs can achieve a comparable pulsed performance to conventional quantum cascade lasers. In particular, the device has a threshold current density of 3 kA/cm2, an output power of 0.47 W, and a total wall-plug efficiency of 4.5% in pulsed mode. Optimized electron extraction and the prevention of thermal backfilling allow higher duty cycles, operation up to 10%, with 15 mW average output power at room temperature without optimization of the laser cavity or coatings. At zero bias, the device has a responsivity of around 40 mA/W and a noise equivalent power of 80 pW/Hz at room temperature, which in on-chip configuration outperforms conventional uncooled discrete detectors.