Extend the thermal model to capture full-timescale chirp dynamics

Extend the simplified two-node thermal model for terahertz quantum cascade lasers by coupling it with carrier–photon rate equations so that sub-microsecond transients and chirp dynamics across the full picosecond-to-millisecond timescale can be explained.

Background

The paper models microsecond-to-millisecond frequency chirp in pulsed terahertz quantum cascade lasers using a two-node thermal model that describes heating of the active region and heat transfer to the substrate and heat sink. This model reproduces the overall thermal chirp trend and the observed chirp reversal.

The authors explicitly identify a limitation: carrier–photon dynamics on sub-microsecond timescales are omitted and cannot be accounted for by the current model. They indicate that coupling the thermal equations to carrier–photon rate equations is needed to describe the complete picosecond-to-millisecond transient evolution.