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 μm 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 ${\mathrm{cm}}^{\text{−1}}$ and the differential gain to be ${\text{3×10}}^{\text{−15}}{\text{–1×10}}^{\text{−16}}\hspace{0.5em}{\mathrm{cm}}^2,$ 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.