Confinement-enhanced biexciton binding energy in semiconductor quantum dots

Experimental observation of the ground-state biexciton transition in ${\mathrm{CdS}}_{\mathit{x}}$ ${\mathrm{Se}}_{1\mathrm{-}\mathit{x}}$ quantum dots in glass is presented in a three-beam experiment, involving a probe, a pump, and a saturating laser pulse. The observed quantum-dot biexciton ground state has a strongly enhanced binding energy compared to the bulk as theoretically predicted. The biexciton binding energy is measured as a function of quantum-dot size and the results are compared with calculations.