  The optical properties of single InAsP/InP quantum dots are investigated by
spectrally-resolved and time-resolved photoluminescence measurements as a
function of excitation power. In the short-wavelength region (below 1.45
$\mu$m), the spectra display sharp distinct peaks resulting from the discrete
electron-hole states in the dots, while in the long-wavelength range (above
1.45 $\mu$m), these sharp peaks lie on a broad spectral background. In both
regions, cascade emission observed by time-resolved photoluminescence confirms
that the quantum dots possess discrete exciton and multi-exciton states. Single
photon emission is reported for the dots emitting at 1.3 $\mu$m through
anti-bunching measurements.
