Abstract
Hot carrier dynamics in plasmonic nanorod metamaterials and its influence on the metamaterial's optical Kerr nonlinearity is studied. The electron temperature distribution induced by an optical pump in the metallic component of the plasmonic metamaterial leads to geometry‐dependent variations of the optical response and its dynamics as observed in both the transmission and reflection properties of the metamaterial slab. Thus, the ultrafast dynamics of a metamaterial's optical response can be controlled via modal engineering. Both the transient response relaxation time and magnitude of the nonlinearity are shown to depend on the modal‐induced spatial profile of the electron temperature distribution and the hot‐electron diffusion in nanorods. The nonlocal effects, depending on the excitation‐induced losses in the metal, are shown to dictate the modal structure of the metamaterial slab and the associated dynamics of its nonlinear response. The opportunity of controlling the electron temperature profile induced in the plasmonic nanorods by changing the metamaterial's geometry and/or excitation conditions paves the way to achieve controllable dynamics of the nonlinear optical response for free‐space as well as integrated nanophotonic applications involving nonequilibrium electrons.
Highlights
Fast electron temperature profile induced in the plasmonic nanorods by changing the metamaterial’s geometry and/or excitation conditions paves the way to achieve controllable dynamics of the nonlinear optical response for free-space as well as integrated nanophotonic applications involving nonequilibrium electron–electron and electron-phonon scattering processes establish the thermalized electron distribution described by the increased temperature, before the residual electron energy is transferred to lattice
We have studied the hot-electron dynamics and diffusion in plasmonic nanorods forming a metamaterial composite
A microscopic model allows us to take into account the nonuniform profile of the electron temperature distribution within the nanorods, which depends on the modal distribution at the excitation wavelength and determines the magnitude and the dynamics of the transient nonlinear response
Summary
We consider a plasmonic metamaterial geometry consisting of an assembly of gold nanorods embedded in a porous alumina (AAO) matrix and supported by a transparent substrate (Figure 1a). The nanorods, vertically aligned in the z-direction in the Cartesian frame of Figure 1a, form a uniaxial metamaterial that can be represented within the effective medium theory (EMT) by a diagonal permittivity tensor of the form ε = diag[εx, εy = εx, εz], where the spectral dependence is implicit and the z-direction is along the optical axis of the metamaterial. P)ε h p)ε h and εz = pεAu + (1 − p)εh, where p = π(r/d) is the nanorod concentration, with r and d being the nanorod radius and the average separation between nanorods respectively, εAu and εh are the permittivities of Au and the host medium (anodized aluminium oxide, AAO), respectively.[16] This model is valid, in general, away from the Brillouin zone edges of the nanorod array of period d, but fails to accurately reproduce the optical response of the metamaterial when losses are “small,” in which case the nonlocal corrections to the effective medium theories need to be considered.[11,13]. It should be noted that these spatial-dispersion effects are automatically taken into account in the numerical simulations of the composite nanorod metamaterial which do not rely on effective metamaterial parameters
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
