Time-resolved nonlinear luminescence of excitons and bi-excitons in Zn
Se-based single quantum wells has been studied by means of a sub-picos
econd excitation correlation technique. The enhancement in luminescenc
e efficiency of bi-excitons was clearly observed in a time-correlation
trace of nonlinear bi-exciton luminescence. The origin of the enhance
ment was attributed to the higher-order nonlinearity with respect to t
he density of bi-excitons, and was explained by considering the stimul
ation of bi-exciton luminescence.