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

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