Differential transmission spectroscopy (DTS) in Cu2O in the presence of cold excitons

A high density of cold 1s orthoexcitons was created in Cu2O using two count erpropagating high-power femtosecond infrared (IR) laser beams tuned to hal f the 1s exciton resonance energy. The initial 1s exciton gas density was e stimated to reach up to 10(20) cm(-3). The resulting differential absorptio n spectrum revealed a pronounced screening of the yellow np absorption line s, up to complete disappearance of the 2p exciton for the highest pump inte nsity. On the other hand, no change in the n = 1 phonon-assisted absorption continuum was detected, showing that the Mott condition for dissociation i nto a two-component plasma was not reached for the n = 1 excitons.