Highly temperature insensitive, deep-well 4.8 μm emitting quantum cascade semiconductor lasers

4.8 mu m emitting, quantum cascade (QC) lasers that suppress carrier leakage out of their active regions to the continuum have been realized by using deep (in energy) quantum wells in the active regions, tall barriers in and around the active regions, and tapered conduction-band-edge relaxation regions. The characteristic temperature coefficients T-0 and T-1 for the threshold current density J(th) and slope efficiency, respectively, reach values of 238 K over the 20-60 degrees C temperature range, which means that J(th) and the slope efficiency vary with temperature half as fast as those of conventional QC lasers. In turn, significantly improved continuous wave performance is expected.