Differential Transmission Spectroscopy (DTS) in Cu2O in the Presence of Cold Excitons

Abstract : A high density of cold 1s orthoexcitons was created in Cu2O using two counterpropagating high-power femtosecond infrared (IR) laser beams tuned to half the 1s exciton resonance energy. The initial 1s exciton gas density was estimated to reach up to 1020 cm - 3. The resulting differential absorption spectrum revealed a pronounced screening of the yellow np absorption lines, up to complete disappearance of the 2p exciton for the highest pump intensity. On the other hand, no change in the n = 1 phonon-assisted absorption continuum was detected, showing that the Mott condition for dissociation into a two-component plasma was not reached for the n = 1 excitons.