High performance injectorless quantum-cascade lasers

Injectorless quantum-cascade (QC) lasers, for the first time comparable to conventional QC lasers, are presented. The samples are based on InP and the active region is designed as a four-level staircase, realised in the strain-compensated material system Ga_0.4In_0.6As/Al_0.56In_0.44As. Low threshold current densities and a maximum operating temperature of 350 K have been achieved, due to an optimised design. At 77 K the wavelength is about 10 μm, while threshold current densities of 0.9 kA/cm² have been observed, which compare well with those of conventional QC lasers in this wavelength region.