Characterization and analysis of single-mode high-power continuous-wave quantum-cascade laser

We measured and modeled the performance characteristics of a distributed-feedback quantum-cascade laser exhibiting high-power continuous-wave (CW) operation in a single spectral mode at lambda approximate to 4.8 mu m and temperatures up to 333 K. The sidemode suppression ratio exceeds 25 dB, and the emission remains robustly single mode at all currents and temperatures tested. CW output powers of 99 mW at 298 K and 357 mW at 200 K are obtained at currents well below the thermal rollover point. The slope efficiency and subthreshold amplified spontaneous emission spectra are shown to be consistent with a coupling coefficient of no more than kappa L approximate to 4-5, which is substantially lower than the estimate of 9 based on the nominal grating fabrication parameters. (c) 2005 American Institute of Physics.