Lasing in 9.6-$\mu$m quantum cascade lasers

Lasing in MBE-grown impulsively pumped quantum cascade lasers of 9.6 $\mu$m at 140 K has been demonstrated. The active area is based on three-phonon resonance scattering of electrons. An In$_{0.53}$Ga$_{0.47}$As/Al$_{0.48}$In$_{0.52}$As solid alloy heteropair was used to form periods of quantum cascade lasers. The upper In$_{0.52}$Al$_{0.48}$As cladding of the waveguide was made thick. Alloyed and unalloyed lower metallization systems were studied. The threshold current density for a ridge laser 1 mm long and 27 $\mu$m wide has been found to roughly equal 3 kA/cm$^2$ at 87 K. The optical output power has been estimated at a level of 20–35 mW.