Femtosecond dynamics and absorbance of self-organized InAs quantum dots emitting near 1.3 μm at room temperature

High-sensitivity, femtosecond differential transmission measurements on self-organized InAs quantum dots at room temperature allow us to determine the dynamics of resonantly excited electron-hole pairs, as well as the absorbance (α₀d) of quantum dots. The room temperature differential transmission signal decreases with a time constant of 65 ps, determined by the rate of excitation from the initial photoexcited states to higher excited states. From the magnitude of the differential transmission, we deduce that the absorbance, and hence the maximum gain/pass in the direction normal to the layers, is ≈ 2.1 × 10^-3 at the spectral peak for our sample with six layers of quantum dots.