# Thinfilm Hybrid Nanostructures: A Perspective to Subcycle Opto-Electronics and Coherent Control
## 1 Introduction  
The development of plasmonic assisted sensors is a hot topic in research and provides broad range of applications driven by biomedical sensing and lab-on-a-chip applications [1; 2; 3]. Tailored geometries demonstrate complex dynamic behavior for improved sensing and electrooptical coupling. Especially their properties under broken symmetry [4] and the formation of whispering gallery modes [5] determine new routes in the developemnt of tailored plasmonic structures and their time dynamic behavior. The availability of ultrafast time-resolved spectroscopy methods of light and electrons enabled the investigation of dynamics on timescales down to attosecond duration [6; 7; 8] not only in the gas phase, but also in solid samples. However, the combination of ultrafast time resolution and nanometer spatial resolution is experimentally challenging and facing a nearly unexplored field in experimental ultrafast science. In 2007 [PERSON] et al. proposed the attosecond nanoplasmonic field microscope [9]. [PERSON] et al. demonstrated the technique of attosecond photocopy [10]. Both concepts theoretically demonstrate that ultrafast science at ultrasmall structures with high temporal and spatial resolution down to attosecond duration and nanometer spatial resolution is feasible and experimentally accessible. Imaging electric fields on the nanoscale has been demonstrated by several groups [11; 12; 13; 14] and even the dynamic behaviour has been retrieved by [PERSON] et al. [15] and [PERSON] et al. [16; 17] imaging the plasmonic fields of a propagating plasmon on a silver grating and in silver nanowires, respectively, by interferometric time-resolved photoelectron emission micrographs (ITR-PEEM). Resolving the time dependent behaviour of plasmonic systems has been limited to the spectral domain for a long period of time. The availability of ultrafast laser pulses in the femto- and even attosecond range provides access to the realtime measurements of these dynamics following new excitation schemes [18]. Even more complex nanostructures as coupled particles, resonators, or coupled antenna structures exhibiting complex dynamic temporal as well as spatial modulations of the electric field on subcycle time scale [15; 16; 19] are in the focus of current research. [PERSON] et al. [20] describe in the model of plasmon hybridization the spatial characteristics of complex nanostructures under resonant excitation. Plasmonic coupling in hybrid nanoscopic systems builds up a symmetrical (bright) mode, where the charge density is unilateral modulated as a dipole or an antisymmetrical (dark) mode forming a multipole. [PERSON] et al. [21] demonstrated that the excitation of antisymmetrical modes is only possible from the interaction of bright modes, inhomogeneous far-field illumination or related excitation schemes. The observations presented in this article are related to nearfield phenomena of strongly coupled plasmons which has been discussed by [PERSON] et al. [22]. Besides the strong coupling hybridization is of major importance to explain the formation of whispering gallery modes after excitation and an enhanced lifetime of the plasmon itself. The hybrid structure presented in this paper is comparable to the geometry and study presented by [PERSON] et al. [23] analysing a symmetric tripple layer nano sandwich structure with respect to the excitation and superposition of dark and bright plasmonic modes. With respect to early studies on this topic [24] our studies presented here are focused on ultrafast mode coupling and coherent control on a gold-silica-silver nanodisk system. Nevertheless, we compare our studies again to [PERSON] et al. studying the hybridization in Au-SiO\({}_{2}\)-Au nanodisk sandwic [25] in bulk media and compared extinction measurements to simulations. The sandwiches are composed of two gold disks (radius 55 nm and 44 nm, height 10 nm) that are separated by an insulating silica disk (diameter adapting top and bottom disk, height 10 nm).