Tapered quantum cascade lasers with isolated channel emitting at 9 μm.

We report the improved performance of tapered quantum cascade lasers (QCLs) with a buried heterostructure (BH) operating in a continuous-wave (CW) mode and emitting at 9 μm. The introduction of an isolation channel in the tapered QCL causes the output power decrease more slowly as the driving current changes from the pulsed to CW mode, which is associated with a reduction in thermal resistance. Compared to the Fabry–Pérot structure, the 1° tapered QCL with an isolation channel achieves a horizontal full width at half maximum (FWHM) divergence angle of 25.1°, while the CW mode output power decreases by only 12.02% at 298 K. [ABSTRACT FROM AUTHOR]