With the emergence of quantum technologies for information processing, a major stake is the handling and the control of the quantum properties of light at the nanoscale in planar structures. In this context, metallic nanostructures allowing for the conversion of single photons in single surface plasmons (collective oscillations of electrons), offer very promising opportunities. So far, experimental demonstrations have been limited to punctual or unidimensional nanostructures, mainly fabricated by physical processes, where plasmons often undergo high scattering losses that limit their use for actual applications.
Researchers from CEMES (NeO and GNS groups), with the contribution of colleagues from ETH Zürich (Switzerland), have used an ultrathin cavity made of crystalline gold coupled to a single quantum nanosource emitting photons in a wide spectral window in the visible (600-800 nm), aiming at demonstrating a spatial and spectral filtering of the single plasmons that propagate in the structure over several micrometers.
The photons emitted one by one and randomly between 600 < λ < 800 nm by a single NV colored center hosted by a nanodiamond positioned in the direct vicinity of the metallic structure are transferred in the near field to the continuum of available plasmon modes of the cavity. By imaging their propagation as a function of the wavelength, the authors have shown that the two-dimensional distribution of the signal in the hexagonal cavity is driven by the dissipation related to absorption losses.
In a second step, the gold crystalline platelet has been carved by a focused ion beam (FIB) with the inclusion of a plasmonic Bragg mirror optimized at a given wavelength. This periodic structure has provided a new channel for the wavelength-dependent redistribution of the optical signal within the hexagonal cavity. The observations of this "single plasmon sieve" effect have been numerically confirmed by using the formalism of the Green Dyadic function with the simulation of the plasmonic transmittance of the signal emitted by a localized dipolar source.
The results obtained with this hybrid system, made of a single photon nanosource and a plasmonic 2D cavity, are a first step demonstrating the potential of platelets in crystalline gold for the development of more complex multi-inputs/outputs circuits for information processing with for instance the optical interconnexion between several quantum nanosources in a planar architecture.
This work has been funded by the projects NanoX PlasQuant (ANR-17-EURE-0009), ANR PlaCoRe (ANR-13-BS10-0007) et CALMIP P1107.
Publication
" Single plasmon spatial and spectral sorting on a crystalline two-dimensional plasmonic platform " U. Kumar, S. Bolisetty, C. Girard, R. Mezzenga, E. Dujardin and A. Cuche. Nanoscale 12, 13414 (2020)
Contact
Aurélien Cuche aurelien.cuche chez cemes.fr ; Erik Dujardin dujardin chez cemes.fr