Detection and sensing
Nanophotonics enables the control of light-matter interactions on a nanoscale that is much smaller than the wavelength. This makes it possible to trap light in nanoresonators and enhance the efficiency of interactions with matter that would otherwise be very weak.
The team is exploring two avenues of research to improve the efficiency of active components and detection processes:
Plasmonic resonators are of particular importance in the THz range. The objective of this thesis is to use so-called Helmholtz resonators, combined with 2D materials such as graphene, hBN, or MoS₂, to develop electrically tunable devices. In graphene, for example, applying a voltage can modify the Fermi level and thus alter its optical response. When combined with a plasmonic resonator, the modulation of the reflected or transmitted electromagnetic wave would be enhanced, enabling its use as a modulator. The resonator can also be used both to enhance the interaction with matter for broadband infrared spectroscopy and to amplify the photocurrent measured at the graphene interface, which would act as a detector.
Certain biological objects, such as proteins, are particularly small (on the order of a few tens of nanometers), so they scatter very little light: observing them is extremely difficult without certain experimental techniques, such as labeling with fluorescent molecules, which inevitably affects the object being studied. Our team is studying so-called “label-free” methods, based on the iSCAT technique, which seeks to reconstruct images from the interference between a reference wave and the wave scattered by the particle. The scattered field can be enhanced by the presence of nanophotonic objects in its environment: this is the principle behind the CEISCAT method. These activies led to the development of UNVEIL :
UNVEIL : Label-Free Nanoparticle Characterization
Our research aims at developing optical methods for the quantitative characterization of nanoparticles in suspension. We have developed a label-free technique based on interferometric scattering (iSCAT) microscopy, capable of detecting freely diffusing nanoparticles with diameters down to approximately 10 nm.
The method combines iSCAT microscopy with holographic reconstruction based on angular spectrum propagation to recover the three-dimensional distribution of scattering particles. By tracking the Brownian motion of individual nanoparticles, we determine their hydrodynamic diameter, while their optical scattering cross section is measured directly from the interferometric signal. This approach provides quantitative measurements of particle concentration and enables heterogeneous samples to be characterized by clustering particles in the scattering cross section–diameter space.
Current applications include the characterization of biological nanovectors such as bacteriophages, lipid nanoparticles (LNPs), extracellular vesicles (EVs), and viruses, with particular emphasis on assessing their full/empty state and population heterogeneity.
Ongoing research focuses on extending the sensitivity of the technique toward weakly scattering nanoparticles, such as bacterial extracellular vesicles, and on developing advanced scattering models to extract richer structural information beyond particle size, including insights into nanoparticle composition and internal organization.
This research has led to several patents and to the creation of Unveil, a spin-off of the Institut d'Optique Graduate School founded in 2025 by Matthieu Greffet, Alexis Auchère, and Jean-Jacques Greffet. While Unveil develops instrumentation based on these technologies, research on the underlying methods continues within the laboratory.
 | Pierre-Louis Paillet Doctorant (PhD 2027) Active resonators coupled to 2D materials for detection and sensing in the THz range |
 | Alexis Corbillet Doctorant (PhD 2028) Label-free detection of single nanometric biological objets |
| Matthieu Greffet Ingénieur de recherche UNVEIL |
| Florian Semmer Post-doctorant (maintenant ingénieur de recherche chez UNVEIL)
|