INGAAS-GAAS QUANTUM-DOT LASERS

Quantum-dot (QD) lasers provide superior lasing characteristics compar ed to quantum-well (QW) and QW wire lasers due to their delta like den sity of states, Record threshold current densities of 40 A.cm(-2) at 7 7 K and of 62 A.cm(-2) at 300 K are obtained while a characteristic te mperature of 385 K is maintained up to 300 K. The internal quantum eff iciency approaches values of similar to 80%. Currently, operating QD l asers show broad-gain spectra with full-width at half-maximum (FWHM) u p to similar to 50 meV, ultrahigh material gain of similar to 10(5) cm (-1), differential gain of similar to 10(-13) cm(2) and strong nonline ar gain effects with a gain compression coefficient of similar to 10(- 16) cm(3). The modulation bandwidth is limited by nonlinear gain effec ts but can be increased by careful choice of the energy difference bet ween QD and barrier states, The linewidth enhancement factor is simila r to 0.5. The InGaAs-GaAs QD emission can be tuned between 0.95 mu m a nd 1.37 mu m al 300 K.