Non-linear optics of free atoms and molecules

Non-linear optics studies the phenomena which ocurs when a very intense light beams interact with matter. Using dynamical and density matrix methods, we compute the third order susceptibility to describe the non-linear relation between polarization field and electric field. Also we give the definition of the Raman effect and a few applications in alkali vapours using Stimulated Electronic Raman Scatering (SERS). Finally, a general introduction to Coherent Anti-Stokes Raman Scattering (CARS) and its applications in thermometry is also presented. (author). 1 fig