Linewidth enhancement factor of quantum cascade lasers with single phonon resonance-continuum depopulation structure on Peltier cooler

The linewidth enhancement factor (alpha-factor) of a commercially available 6.1 mu m InGaAs/InAlAs distributed-feedback quantum cascade laser capable of continuous-wave operation with a Peltier cooler and its current dependence were investigated. a tended to increase slowly with an increase in current. alpha, probably affected by detuning, was still smaller than that of conventional 1.55 mu m semiconductor laser diodes.