Multiple-photon spectrum of CdS semiconductor quantum dot for bioimaging

We study the dynamic processes of multiple-photon absorption and emission in a semiconductor quantum dot. By the non-perturbative time-dependent Schrödinger equation, it is shown that electrons in the quantum dot can be optically excited from the valence band to the conduction band via multiphoton processes, leaving holes in the valence band. The radiative recombination of the conduction-band electrons with the valence-band holes results in optical emission of a single photon having an energy which is larger than the input photon energy, resulting in the high-photon-energy luminescence from the quantum dot activated by low-energy photons to emit radiation in the visible optical regime for bioimaging application.