Quantum Dot Laser Threshold Gain

Self-assembled quantum dots make imperfect emitters: no two dots are exactly the same size, so their ground-state transition energies scatter around a mean — inhomogeneous broadening. This simulator models a quantum-dot laser's active region as an ensemble of discrete two-level dots, each with its own occupation state, and integrates real carrier and photon rate equations frame by frame. Pump current fills dot states until the population-inversion factor turns net gain positive; raise the cavity loss and you need more current (or more dots, or tighter size control) to cross it. Watch the dot field brighten as occupation rises, and cavity photons appear and cascade once modal gain overtakes loss — the lasing threshold, visualized directly instead of just plotted.