In this study, the four-wave mixing (FWM) spectrum of a strongly pumped hybrid structure is theoretically examined. The hybrid structure consists of an asymmetric double semiconductor quantum dot (SQD) molecule and a spherical metal nanoparticle (MNP), which are coupled together via long-range Coulomb interaction. Having as a starting point the Hamiltonian of the system, in the dipole and the rotating-wave approximations, we derive a set of nonlinear density matrix equations, which are

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... ly solved, in the steady-state limit, and then the FWM coefficient is calculated within a range of values of the pump-probe field detuning. The spectral response of the FWM coefficient is investigated, for different values of the pump-field detuning, the electron-tunneling rate and the energy gap between the upper states in the energy-level scheme of the double SQD molecule, while the interparticle distance between the two components of the structure is modified. Keywords: asymmetric quantum-dot molecule; density-matrix equations; hybrid structure; metal nanoparticle; pump field; probe field; four-wave mixing Publisher's Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.