Gain dynamics and spectral hole-burning in In(Ga)As self-organized quantum dots

The dynamics of spectral hole burning, gain saturation and carrier capture are important in the design of semiconductor QD lasers and amplifiers, especially in high speed applications. Using femtosecond three-pulse white light pump and probe differential transmission spectroscopy, we have observed spectral hole burning in both the excited and ground states, which directly shows the carrier relaxation between the discrete energy levels in QDs with a population inversion. The gain recovery due to both relaxation of confined excited states and carrier capture are observable in our spectrally and temporally resolved experiments