Quantum Dot Laser Threshold Gain — Spectral Gain & Phase Portrait (2D)

This 2D companion to the 3D quantum-dot laser cavity simulator integrates the identical carrier and photon rate equations, but visualizes them through two native 2D representations instead of a 3D particle cavity. The top panel plots the inhomogeneously-broadened spectral gain lineshape directly: its peak at zero detuning is exactly the modal gain, so you can see gain versus loss as two curves crossing, and watch the peak flatten as size dispersion widens. The bottom panel is a phase portrait of carrier occupation against photon density, tracing the live trajectory as it settles toward its operating point and crossing a dashed threshold-occupation line the moment modal gain overtakes cavity loss. Tune pump current, cavity loss, dot-size dispersion and areal dot density to find — and cross — the lasing threshold.