Laboratoire Interdisciplinaire de Physique

How to measure objects that cannot be seen under normal circumstances? There is a way to modify the beam of a laser so that it provides exactly the information desired despite the presence of an environment that can be complex and messy. Moreover, this procedure does not work in an approximate way, but in an optimal way in the physical sense of the term: nature does not allow for better measuring accuracy with the coherent light of a laser.

The action potential is the fundamental signal of neuronal cells. In mammalian neurons, this signal is generated in the initial segment of the axon by a fast sodium current mediated by voltage-gated sodium channels. Luiza Filipis and Marco Canepari have developed a unique method allowing the measurement of the sodium current in the axon initial segment during the action potential generation. This novel technique opens the gate to the full understanding of neuronal excitation and to the investigation of genetic diseases caused by neuronal excitability dysfunction.

Observing objects hidden behind scattering layers is a problem of general interest for biomedical applications, or in aerial, terrestrial and naval transport control and security. In optics, an opaque layer is such that each source point of the object of interest gives rise to a speckle figure, which spreads out over the entire field of view, making the source points non-localizable. We have shown, theoretically and experimentally, that it is possible to measure the diffusion coefficient of micrometric fluorescent beads hidden behind a totally scattering layer.