Room-temperature gain and differential gain characteristics of self-assembled InGaAs/GaAs quantum dots for 1.1-1.3 μm semiconductor lasers

This letter presents an explanation of the optical gain and differential gain of two types of self-assembled quantum dots in the laser active region, which shows 1.16 and 1.31 mu m spontaneous emission from the ground state at room temperature. The gain spectrum was measured using the Hakki-Paoli method up to the lasing threshold. The maximum optical gain of the ground state was found to be 150-400 cm(-1) and the differential gain to be 3x10(-15)-1x10(-16) cm(2), which agrees quite well with the calculation, taking into account both homogeneous broadening and inhomogeneous broadening. Our results will be a guide to the design of laser structures. (C) 2000 American Institute of Physics. [S0003-6951(00)02932-6].