Biophotonics

Neurostimulation has been approved for the treatment of several debilitating conditions. It is one of the fastest-growing areas of medicine owing to its potential as a therapeutic solution. Nowadays, electrical means to stimulate neural tissue or to record compound neural action potentials are still the gold standards for neuroprosthetics and neuromodulation devices. They however have several limitations such as current spreading or MRI incompatibility. 

In this project we are studying optical stimulation and sensing techniques that could overcome these limitations for the development of the next generation of minimally invasive, high-resolution implants.

For decades, optical microscopy has played an important role in the observation of cells in biology. As for all imaging optical system, the spatial resolution of microscopes is however limited. Several new approaches have been developed to overcome this limit, particularly in fluorescence microscopy. We investigated the use of saturation of the two-photon absorption fluorescence excitation for improving the resolution. 

   Harmonics in the saturated fluorescence signal                                        Resolution improvement
                for increasing incident power

The saturation of the excitation probability of fluorophores induces a strong nonlinear fluorescence response which can be used to retrieve structural information from a volume smaller than the non-saturated excitation point spread function.