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International audienceTerahertz electromagnetic waves propose attractive features such as non-invasive and non-destructive analysis, transparency and good penetration depth through various materials, low scattering and broad spectral bandwidth. In this paper, we demonstrate the capability of terahertz imaging for the investigation of art paintings. The imaging system is able to reveal buried layer information such as a graphite handmade sketch covered by several layers of painting. In addition, taking advantage of the pulsed terahertz emission, we show that it is also possible to evaluate the variations of the painting thickness

We report the direct observation of the formation and stabilization of radical cations of trans-stilbene and 1,4-diphenylbutadiene (DPB) in polar solvents (acetonitrile, linear alcohols) by picosecond "pump-probe" and polarization sensitive resonant CARS experiments. For the first time we have observed the formation and stabilization rate of the DPB radical cation, which occurs on a 10-20 ps time scale. We confirm that the formation process is mainly monophotonic and depends on the polarity of the solvent but found no correlation between the formation and stabilization rate and the solvent dielectric relaxation time.

3D terahertz computed tomography has been performed using a monochromatic millimeter wave imaging system coupled with an infrared temperature sensor. Three different reconstruction methods (standard back-projection algorithm and two iterative analysis) have been compared in order to reconstruct large size 3D objects. The quality (intensity, contrast and geometric preservation) of reconstructed cross-sectional images has been discussed together with the optimization of the number of projections. Final demonstration to real-life 3D objects has been processed to illustrate the potential of the reconstruction methods for applied terahertz tomography.