The simultaneous measurement of the xxz and zzz components of the quadratic susceptibility of Non Linear Optical functionnalized polymer films is performed by Fabry Perot under Oblique Incidence technique.Precise results are obtained without any accurate knowledge of the complex dielectric constant and the thickness of each layer.The deorientation of a non linear optical unit is compared in three main chain functionnalized polyurethanes at a constant difference of temperature below the glass transition temperature. Independently of the absolute value of the Tg, the rate of deorientation is very dependant of the monomer structure.
