Optimal control of light propagation and exciton transfer in arrays of molecular-like noble-metal clusters

Abstract: We demonstrate theoretically the possibility of optimal control of light propagation and exciton transfer in arrays constructed of subnanometer sized noble-metal clusters by using phase-shaped laser pulses and analyze the mechanism underlying this process. The theoretical approach for simulation of light propagation in the arrays is based on the numerical solution of the coupled time-dependent Schr\"odinger equation and the classical electric field propagation in an iterative self-consistent manner. The electronic eigenstates of individual clusters and the dipole couplings are obtained from ab initio TDDFT calculations. The total electric field is propagated along the array by coupling an external excitation electric field with the electric fields produced by all clusters. A genetic algorithm is used to determine optimal pulse shapes which drive the excitation in a desired direction. The described theoretical approach is applied to control the light propagation and exciton transfer dynamics into a T-shaped structure built of seven Ag8 clusters. We demonstrate that a selective switching of light localization is possible in $\sim$5 nm sized cluster arrays which might serve as a building block for plasmonic devices with an ultrafast operation regime