Spatiotemporal control of an ultrashort pulse

When an ultrashort pulse of light illuminates a multiple scattering sample, such as a paint layer, the output light suffers both spatial and spectral mixing. Spatially, the output intensity is a multiple interference pattern also known as speckle. In the spectral domain, each wavelength of the input pulse will experience a different interference figure because of the scattering. The exact same vision in the temporal domain leads to a broadened pulse, with an average characteristic time much longer than the time-width of the input pulse.

We have developed a transmission matrix approach to coherently control either every wavelength of the output pulse (Multispectral Transmission Matrix)  or every arrival time of the output pulse (Time Resolved Transmission Matrix). Using this information in addition with a unique spatial light modulator, we have notably shown a retrieval of the ultrashort pulse after propagation through a thick scattering medium, as well as a control of its temporal behavior in an arbitrary spatial position outside the sample. These approaches could lead to enhance non-linear phenoma or to probe light-matter interactions in highly disordered systems.