Quantum Cascade Lasers in the InAs/AlSb Material System

We review the current state of the InAs/AlSb quantum cascade laser (QCL) technology. These materials have brought significant progress in short wavelength QCL due to the high-conduction band offset. The first QCLs emitting below 3 μm have been demonstrated in this system. The short wavelength limit of QCL operation has further been moved down to 2.6 μm. This system is also well suited for far-infrared QCLs because high intersubband gain can be achieved at low transition energies due to the small electron effective mass in InAs. Room temperature operation has been demonstrated in InAs-based QCLs to a wavelength of 21 μm, for the first time for any semiconductor laser emitting above 16 μm. Both short- and long-wavelength single-frequency distributed feedback InAs/AlSb QCLs have been realized, as well as widely tunable external cavity sources for the 3-3.5 μm spectral range.