Multiphoton excitation of quantum dots by ultrashort and ultraintense laser pulses

Multiphoton optical processes in semiconductor quantum dots (QDs) excited by ultrafast (femtosecond) and ultraintense (GW/cm(2)) lasers are considered as the ultimate tags for cellular bioimaging. By solving the time-dependent Schrodinger equation unperturbatively, experimentally observed strong multiphoton excitation is reproduced when optical transitions among all confined states and a few hundred more extended states are taken into account. Model calculations indicate a significant excitation of a CdS QD of 3.7 nm in radius by a 100 fs laser pulse with a 10 GW/cm(2) peak optical power. The excitation rate is almost constant between 1300 and 560 nm, a useful region for bioimaging. (c) 2006 American Institute of Physics.