Nonlinear Quantum Plasmonics: A Quantum Hydrodynamic Approach
Technical Report,01 Mar 2017,28 Feb 2019
Fondazione Istituto Italiano di Tecnologia Genova Italy
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In this project we have developed a new theoretical model for the nonlinear electrodynamic response at metal surfaces and obtained a numerical implementation of such model suitable for arbitrarily shaped geometries. Our approach is based on the quantum hydrodynamic theory QHT, which allows to include spatially dependent electron density profiles in order to account for spill-out effects at the boundaries of a metallic system. The accuracy of the QHT however is based on the energy functionals used to describe the free-electron gas internal energy. We have developed a numerical implementation for multi-shell structures and compared QHT results to time-dependent density functional theory TDDFT calculations for systems in which quantum tunneling or quantum size effects could not be neglected. The generality of the QHT approach allowed also to consider nonlinear dynamics of free electrons. We have expanded for the first time the QHT equations beyond the linear approximation and performed second-harmonic generation SHG calculations for metallic slabs and cylinders and compared the QHT results to experimentally measured efficiencies. Moreover, we have investigated the spectral dependence of the SHG process and found resonances induced by the spill-out of the electron density at the metal surface that could in principle increase the SHG efficiency by several order of magnitude.
- Electrooptical and Optoelectronic Devices