Effects of exciton–biexciton coherent coupling on exciton absorption in quantum dots

We report unusual excitonic absorption spectra with dip-shaped structures caused by exciton–biexciton coherent interactions in quantum dots. The exciton absorption spectrum is measured with the micro-photoluminescence excitation technique in a single InGaAs quantum dot. The spectrum changes from Lorenztian-shaped to dip-shaped with increasing excitation intensity. A theoretical analysis with the density matrix method reveals that exciton–biexciton coherent interactions create dressed states in the exciton–biexciton system and lead to the unusual absorption spectra.