A unipolar semiconductor laser emitting in the mid-infrared spectral region is demonstrated. The laser scheme relies on a simple three-level system in GaAs/AlGaAs asymmetric coupled quantum wells. Population inversion between excited states is achieved by optical pumping of electrons from the ground state with a CO2 laser. Long-wavelength (≈15.5 μm) laser emission is demonstrated. The laser is operated in the pulsed regime up to a temperature of 110 K and with an output peak power ≈0.4 W at 77 K. Unipolar quantum well semiconductor lasers based on this principle are capable of covering the long wavelength mid-infrared spectral region above 12 μm.

We demonstrate operation of a high-power quantum fountain unipolar laser relying on intersubband emission in optically pumped GaAs/AlGaAs quantum wells. The collected power per facet is as large as 2.3 W at 20 K and 1.5 W at 120 K, which translates into 6.6 W optical power per facet at low temperature accounting for collection efficiency. The maximum operating temperature is 135 K. We also demonstrate that the lasing wavelength can be tuned by as much as Δλ/λ≈2.5% simply by tuning the pump wavelength.