Improved performance of GaAs-AlGaAs superlattice quantum cascade lasers beyond /spl lambda/=13 μm

Highly improved quantum cascade lasers based on intraband transitions in a chirped AlGaAs-GaAs superlattice have been realized. Lasing in a liquid nitrogen environment with a laser wavelength centered at 13 μm and with a peak optical power per facet exceeding 80 mW is achieved. A threshold current density of 8.6 kA/cm² at 80 K has been measured. Multimode lasing spectra ranging from 12.4 to 13.3 μm and single mode spectra in a short cavity at 13 μm are obtained. To improve the gain in the structure, the design of the injector is optimized. The minibands in the active region are more strongly confined beneath the conduction band edge of the barriers to decrease electron losses into the continuum. The maximum operating temperature exceeds 230 K with T₀ values of 170 K.