Reconfigurable Colloidal Plasmonic Circuits – PlaCoRe

Plasmonic co-planar systems appear to be a good candidate to elaborate the elementary building blocks of ultra-compact optical circuits. However, existing prototypes are mostly fabricated by top-down methods and based on fixed geometries that “freeze” the available plasmons states. The incoming information is thus encoded in the incident light (polarization and wavelength), reducing the degrees of freedom of the system. These limitations, coupled to energy dissipation due to poor crystalline quality of the structures, prevent the elaboration of complex and versatile systems for optical information processing.
The PlaCoRe project proposes an alternative strategy that lies on the development of plasmonic components designed from highly crystalline and mobile colloidal assemblies. Indeed, coupling elementary plasmonic building blocks increases the number of available plasmons states, and by consequence, modifies the Surface Plasmon Local Density of States (SP-LDOS) supported by the structures. In this way, novel plasmonic information processing and original applications can be imagined by controlling this quantity in designing two-dimensional geometries of colloidal assemblies on a dielectric surface. In addition, the control and the “on-demand” modification of the SP-LDOS will allow the access to new functionalities including (i) plasmonic transmittance between two selected locations (input-output concept), (ii) routing of the signal, (iii) coupling with quantum systems (fluorescent nano-emitters), and finally (iv) a new concept of plasmonic logic gates working even at the single photon-plasmon level. PlaCoRe gathers chemists, physicists and theoreticians from 3 leading groups in plasmonics (CEMES Toulouse, ICB Dijon and Inst. Néel Grenoble) to develop reconfigurable plasmonics on this basis. Items (i) to (iv) will be successively addressed on two different colloidal based plasmonic architectures.
The first category will be based on a combination of top-down and bottom-up elaboration techniques that appears as a very appealing new avenue for reconfigurable plasmonics able to produce efficient and controllable light transfer and routing functions. Nowadays, various approaches for manipulating physical nanostructures, including near-field probes, optical, electrostatic and dielectrophoretic methods are available. We will used one of these techniques for the mechanical manipulation of the mobile components of the devices (i.e. long metallic nanowires) but also the functionalized plasmonic tips obtained as a part of the ANR PLASTIPS project (2009-2013).
The second one will be exclusively a colloidal approach in which a set of preselected building blocks (multimodal gold or silver platelets, long metallic wires, nanorods) will be organized at the surface of the sample to tailor, via the SP-LDOS map, delocalized plasmon modes on large area. This part will be the cornerstone of the project because it will be used to realize logic functions from the modal control of the surface plasmons sustained by the whole architecture. At this level, at least two different experimental techniques will be implemented to map the SP-LDOS. It may be, on the one hand, the TPL scanning imaging method, and the scanning near-field optical microscope (SNOM) working with a single light emitting center.