Terahertz quantum cascade lasers with large wall-plug efficiency

Improved optical power performance of bound-to-continuum quantum-cascade lasers operating at 2.83 THz is reported. Peak optical powers of 100 mW at 4 K and power conversion-efficiencies as high as eta(w)=(5.5 +/- 0.4)% in continuous wave at 40 K were measured. The eta(w) values were assessed via an experimental method based on the analysis of the local lattice temperature as extracted by microprobe photoluminescence versus electrical power. From the measured eta(w) values they extracted a slope efficiency value 0.41 +/- 0.11 W/A. (C) 2007 American Institute of Physics.