Peak optical power and thermal performance of quantum cascade lasers

A novel injector design allows to increase the peak optical power of quantum cascade (QC) lasers with GaInAs/AlInAs superlattice active regions. At wavelengths of 8.4 mum peak powers of 2.2 W per facet, corresponding to 88 mW/stage, have been measured at operating temperatures < 80 K. The laser output power grows steadily above threshold with a slope efficiency of 160 mW/A up to currents 6 times larger than the threshold one, displaying the widest reported dynamic range without any sign of gain saturation. In order to measure the facet temperature profile and the active region thermal resistance, a micro-probe band-to-band photoluminescence technique is developed and tested On GaAs/Al0.33Ga0.67As and GaInAs/AlInAs/InP three-wells QC lasers. Comparison between substrate-side and epilayer-side mounted devices shows the superior thermal dissipation capacity of the latter and explains their better performance with respect to threshold current and maximum operating temperature.