Structural and dynamic studies of the polar orientation induced by corona poling and all-optical poling in crosslinkable polymer thin films

International audienceThe fast development of photonics and progress in laser technologies has created the necessity for materials possessing high nonlinear photoactivity. Polymers containing various dye molecules in grafted as well as doped systems have recently been in the limelight of many research groups because of their various potential applications in electro-optic devices and integrated optics, as they possess large second order nonlinear properties, low dielectric constants, the possibility of inducing large nonlinearities, low attenuation and ease of processing. Yet, some important issues concerning temporal stability of induced order and optical loss are still a challenge to researchers. A polymer matrix containing non-centrosymmetric molecules is a macroscopically centrosymmetric solution in which second order nonlinear processes are forbidden due to symmetry reasons. Yet, the system properties may be altered by a non-centrosymmetric external field. In order to create second order nonlinear properties in polymer materials, they have to be prepared with required noncentrosymmetry, which is usually accomplished by poling techniques. Some years ago it was demonstrated that the all optical poling technique permits purely optical orientation of molecules and thus induction of the large second order susceptibilities χ(2). The important advantage of the all-optical technique is that it leads to a periodic ordering of the molecules with the spatial period fulfilling automatically the phase matching condition for second harmonic generation (SHG) [8]. The experiment consists of two phases: the writing (so called ”seeding”) period and the readout one