Univ. Paris-Saclay

Service de Physique de l'Etat Condensé

Laboratory for Electronics and Photonics in Organics (LEPO)
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LEPO gathers the research activities of IRAMIS / SPEC in the physics of near-field Interactions.

Members of LEPO





LEPO carries out research in the field of light-matter interaction at the nanoscale, in particular in nanoparticle assemblies and organized molecular or hybrid systems.

The photonic properties of condensed matter depend as much on the intrinsic properties of its constituents (molecules, crystal lattice,...) as on their organization at nanometric scales. In addition to the design and study of original photonic nano-objects (in collaboration with other material science teams), LEPO's approach is also based on the development of original near-field measurement methods, in order to understand photonic processes at the relevant spatial and temporal scales.

Thus, the group has developed an important know-how in electron photoemission microscopy and in the coupling of optical micro-spectroscopy measurements (absorption, fluorescence, Raman scattering, frequency conversion) with local probe techniques (AFM, STM). Particular attention is paid to AFM, for which an original acquisition mode ("Zero Phase Modulation") is being transfered.

Our main current research projects, described in more detail below, concern local field enhancements in plasmonics, metamaterials or 2D materials, and their applications in advanced imaging and microscopy techniques for biology, biomedical (sensors and phototherapy), optoelectronics, materials ... LEPO is also involed in more prospective topics such as optical manipulation of nano-objects or 1-photon, 1-electron, 1-molecule photonics ...



SINAPSE and UFO projects

Ferroelectric nanocrystals for optical sensing / labeling

We are interested in the optical properties (second harmonic generation, fluorescence) of rare-earth doped BaTiO3 nanocrystals possibly associated with plasmonic nanoantennas. These objects constitute a new class of markers for imaging in biology, with potential applications for the characterization of intraneuronal transport (ANR SINAPSE) or for the detection of extracellular potential change (ANR UFO). Due to their piezoelectric properties, any electrical change in the vicinity of these nanoparticles leads to a modification of their photoluminescence spectrum.

C. Fiorini, S. Vassant

Partners : ENS Paris saclay / LUMIN (coordinator) – F. Marquier / F. Treussart ; Institut Langevin : T. Pons, Lequeux ; IOGS : JJ Greffet, M. Besbes ; CS/SPMS : B. Dkhill, C. Paillard ; ICB : N. Millot ; METSY : F. André, L. Mir




POPCORN project

Photochemistry and photophysics of plasmons for the control of near-field polymerization

POPCORN aims to analyze the relative role of photons (1), charge carriers (2) and heat (3) in plasmon-assisted polymerization at the surface of a metal nanoparticle (NP). To do so, different well-defined reference systems will be considered and a wide range of complementary state-of-the-art temporally-resolved (electron photoemission, dark field spectroscopy) or spatially-resolved (TEM, SERS) techniques will be implemented to reveal the physical processes at stake. POPCORN will open new perspectives in the field of nanofabrication, plasmon-assisted photocatalysis, phototherapy (Photothermal, ROS) or photovoltaics.

C. Fiorini (coordinator), L. Douillard

Partners : IS2M : O. Soppera ; L2N : PM Adam, R. Bachelot ; CEA NIMBE : S. Marguet




POEEMS project

Physics of electron-emitting materials

Objective: to produce electron sources with high emission currents under extreme conditions of electric field, temperature and long-term response.

  • New family of cathode materials: carbon nanotube fiber
  • New emission mechanism: tunneling effect induced by a photoassisted static electric field.

L. Douillard





Influence of a plasmonic antenna on intersystem crossing in a single molecule  

  • 3D nanomanipulation of a gold nanoparticle by local probe, combined with fluorescence analysis by time correlated photon detection.
  • Complete measurement of the different conversion rates according to the presence or the position of the plasmonic nano-antenna that constitutes this gold nanoparticle.

S. Vassant

Partners : S. Marguet (CEA/NIMBE), L. Sosa-Vargas (Sorbone Université)





Self-organized molecular architectures for light emission

  • Van-der-Waals heterostructures based on self-assembled molecular layers on graphene
  • Self-assembled metamaterials using mesophases (crystal-liquid phases) of organic dye derivatives

F. Charra, S. Vassant

Partners : D. Kreher (UVSQ), L. Sosa-Vargas, F. Mathevet (Sorbone Université), AJ Attias (UMI 2B-FUEL)




PHOTOMIC and CANAPO projects

Photochromic organic materials for neuromorphic computing  

  • Optimization of the combined dichroism, birefringence, and photoinduced deformations responses to modulate the optical transmission by a low-power control optical beam.
  • Implementation of this principle as an optical synapse in an all-optical neuromorphic network.

F. Charra (coordinateur Photomic), C. Fiorini

Partners : S. Barbay, L. Calvet (C2N) ; K. Nakatani, R. Métivier (ENS paris Saclay/PPSM)



Laboratory for Electronics and Photonics in Organics (LEPO)

AFM image (in blue) in air at low force on murine Anti-Ovalbumin antibodies (IgG) by tuning fork probe (picture). We can distinguish on the dense interfacial film the local formation of circular multimeric structures with a radius of about 15 nanometers, comparable to that of IgM type antibodies.

DART project

Fast AFM detector in tapping-mode

Atomic Force Microscopy (AFM) is a tool for the investigation of local forces that allows to observe the morphology of a surface. Its versatility allows it to be used in various environments (atmospheric, gas, vacuum, liquid) on a variety of materials including insulators, liquid-solid interfaces and biological surfaces.

In the DART project, we are developing a quartz tuning fork microscope in 0PM-AFM (Zero Phase Modulation) mode that allows for the convenient study of fragile systems in air and liquid environments. Thanks to the high quality factor of the tuning fork probe which provides it with a high sensitivity, we can observe the morphology of three-dimensional films of alkanes on graphite at the atomic scale, or directly characterize in air the structure of the functional films of the biosensors that we make.

Partner : Biophy (Tescan Analytics)




HYDRAE project

Hyperspectral detection of contaminants by surface-enhanced Raman scattering

Surface-enhanced Raman scattering (SERS) is a well-established surface-sensitive technique for detecting the presence of trace amounts of molecular analytes. Within an electromagnetic description, SERS mechanism relies in part on the excitation of localized surface plasmons in random metal films. Surface plasmons generate greatly enhanced electromagnetic fields confined to nanoscale regions known as hot spots. While the impact of surface singularities on plasmonic materials has been widely studied, fabrication of cost-effective efficient SERS substrates remains a challenge. In this project, the correlation between the near and far field optical responses of random metallic SERS substrates fabricated by physical vapour deposition is investigated. Photoemission electron microscopy (PEEM), a high-resolution near-field mapping technique, is used to access statistical properties of the intensity distribution and hot spot localization of evaporated Au films. Thin film evaporation technique constitutes a simple and effective way to quickly prepare and optimize SERS substrates.

L. Douillard

Partners : J.-F. Bardeau (Le Mans Université), Ludovic Duponchel (Université de Lille)



Laboratory for Electronics and Photonics in Organics (LEPO)

The Photoemission Electron Microscope (PEEM) and a PEEM image of a random Au film substrate under 630-nm optical excitation, 10-µm field of view.





Tailored Interfaces and Tunable nano-Architectures engineered at Nanometer Scale

(contact: Fabien Silly )

#2468 - Màj : 17/11/2022


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