Superlattice quantum cascade lasers operating at very long wavelengths (λ≈17 μ)

Summary form only given. Quantum cascade (QC) lasers operating on intersubband transitions between conduction band states in InGaAs/AlInAs heterostructures have proven so far to be extremely versatile, covering the range of wavelengths of the two atmospheric windows (3.4 μm-13 μm). Their extension to even longer wavelengths is, however, problematic, due to the increasingly smaller radiative efficiency of intersubband transitions and to the optical losses from intraband free-carrier absorption, which are roughly proportional to λ. We present the realization of a QC laser employing these so-called "chirped" superlattices and operating at λ~17 μm which represents the first demonstration of a semiconductor injection laser based on intra-band transitions at wavelengths beyond the atmospheric windows. A schematic band diagram of the structure, which has been grown by molecular beam epitaxy (MBE) in the InGaAs/InA1As material system lattice matched to InP substrate is presented