Centre d’Élaboration de Matériaux et d’Etudes Structurales (UPR 8011)

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Upkar KUMAR’s PhD defense

"Plasmon logic gates designed by modal engineering of 2D crystalline metal cavities"

The thesis will be held Wednesday, November 8th 10:30 a.m.
in CEMES Conference Room.



This experimental thesis, conducted in CEMES within the framwork of the ANR project PlaCoRe, explores the potential of spatial and spectral engineering of higher order surface plasmon resonances borne by gold nanoprisms in order to implement antenna, information transfer and logic gate devices.


Jury members

  • Céline Fiorini-Debuisschert, Ingénieur CEA, rapporteur
  • Antoine Moreau, Maitre de Conférences, rapporteur
  • Cyriaque Genêt, Directeur de recherche, examinateur
  • David Guéry-Odelin, Professeur des universités, examinateur
  • Alexandre Bouhelier, Directeur de recherche, invité
  • Christian Girard, Directeur de recherche, invité
  • Erik Dujardin, Directeur de recherche, directeur de thèse
  • Aurélien Cuche, Chargé de recherche, directeur de thèse



The main objective of this PhD work is to design, fabricate and characterize plasmonic devices based on highly crystalline metallic cavities for the two-dimensional information transfer and logical operations. The targeted functionalities are expected to emerge from the spatial and spectral engineering of the high order plasmon resonances sustained by these prismatic cavities. The new building blocks studied in this thesis will pave the way for new strategies in the field of integrated and miniaturized optical information transfer and processing.

First, we thoroughly characterize the optical response of ultra-thin gold colloidal cavities of sub-micronic size (400 to 900 nm) by dark-field spectroscopy (Fig. 1a). The dispersion of the high order plasmonic resonances of the cavities is measured and compared with a good agreement to simulations obtained with a numerical based on the Green Dyadic Method (GDM). We further extend our experiments to systematically tune the spectral responses of these colloidal nanoprisms in vicinity of metallic thin film substrates. This characterization of the plasmonic landscape associated to these crystalline cavities allows us to develop several approaches for an efficient modal engineering.

We systematically study the effects that could potentially affect the plasmonic resonances by non-linear photon luminescence microscopy, which has proved to be an efficient tool to observe the surface plasmon local density of states (SPLDOS). In particular, we show that an effective spatially and spectrally tuning of the high order plasmonic resonances can be achieved by the modification of the substrate (dielectric or metallic), by the controlled insertion of a defect inside a cavity or by the weak electromagnetic coupling between two adjacent cavities.

The rational tailoring of the spatial distribution of the 2D confined resonances was applied to the design of devices with tunable plasmon transmittance between two connected cavities (Figs. 1b,c). The specific geometries are produced by focused ion milling crystalline gold platelets. The devices are characterized by non-linear luminescence mapping in confocal and leakage radiation microscopy techniques. The latter offers a unique way to observe propagating SPP signal over a 2D plasmonic cavity. We demonstrate the polarization-dependent mode-mediated transmittance for devices with adequate symmetry. The results are faithfully reproduced with our simulation tool based on Green dyadic method.

Finally, we extend our approach to the design and fabrication of a reconfigurable logic gate device with multiple inputs and outputs. We demonstrate that 10 out of the possible 12 2-input 1-output logic gates can be implemented on the same structure by choosing the two input and the one output points and by adjusting the threshold of the non-linear luminescence readout signal.