Saturation of intraband absorption and electron relaxation time in n-doped InAs/GaAs self-assembled quantum dots

We have observed the saturation of intraband absorption in InAs/GaAs self-assembled quantum dots. The investigated n-doped self-assembled quantum dots exhibit an intraband absorption within the conduction band, which is peaked at an 8 μm wavelength. The saturation of the intraband absorption is achieved with an infrared pump delivered by a pulsed free-electron laser. The saturation of the transition is observed for an intensity around ≈0.6 MW cm⁻². The electron relaxation time under intraband excitation is measured by time-resolved pump–probe experiments. An electron relaxation time $T_1\text{≈3\hspace{0.05em}}\mathrm{ps}$ is reported.