SPATIAL PROPAGATION OF QUASI-2-DIMENSIONAL EXCITONS IN A LAYERED CRYSTAL BII3 UNDER THE HIGH-DENSITY EXCITATION

Spatial behavior of excitons at high density was studied in a specific exciton system at a quasi-two-dimensional planar defect in layered Bi l(3) crystals. Space- and time-resolved resonance luminescence spectra of the exciton state shows clear blue shift which was delayed in prop ortion to the distance from the exciting spot providing the polariton group velocity. Space- and time-resolved pump-and-probe spectra also s how the blue shift and line broadening not only at the exciting point but at a distant spot away from the exciting point. These spectral cha nges are discussed in terms of high-density exciton-polariton transpor t and the optical Stark effect. (C) 1998 Elsevier Science B.V. All rig hts reserved.