Pump-probe response and four-wave mixing in quantum dot exciton-biexciton - metal nanoparticle hybrid

We investigate theoretically the pump-probe response and the four-wave mixing spectrum in a hybrid system composed of a semiconductor quantum dot coupled to a spherical metal nanoparticle including both ground to exciton and exciton-biexciton transitions. We use a density matrix methodology for the calculation of the absorption/gain, dispersion and four-wave mixing spectra and examine their spectral characteristics, for different interparticle distances and under different pump field detuning conditions with respect to the one-photon and the two-photon resonance transitions. We also analyze the form of the spectra using a metastate theory, a description based on the coupling between the excitonic and the plasmonic transitions, while the dressed-state picture is applied in order to predict the positions at which the spectral resonances arise on the spectra.