Negative differential gain due to many body effects in self-assembled quantum dot lasers

The gain spectrum of a quantum dot laser operating at 1300 nm is studied at high carrier densities, corresponding to dot occupancies of ∼8 e-h pairs per quantum dot. A reduction in peak gain with increasing carrier density is observed, attributed to the saturation of peak gain, yet the continuous increase in dephasing acting to broaden the individual quantum dot transitions.