LOW-THRESHOLD 3 MU-M INTERBAND CASCADE W-LASER

We have demonstrated the operation at lambda approximate to 3.0 mu m o f a 22-stage interband cascade laser with a ''W'' active region for en hanced gain. The threshold current density for a ridge structure is 17 0 A/cm(2) at 80K, and it remains lower than the best reported intersub band quantum cascade laser results at all T up to the maximum lasing t emperature of 225K. At T = 100K, peak output powers up to 532 mW are o bserved, and the slope of 342 mW/A per facet for high injection levels corresponds to a differential quantum efficiency of 1.6 photons emitt ed for every injected electron.