Periodic phase matching and two color holography aspects of the
All Optical Poling of polymers
ERT Cellules Solaires PhotoVolotaïques Plastiques,
Laboratoire POMA - CNRS , Université d'Angers
2 Boulevard Lavoisier, F49045 Angers cedex, France
tel: (33) (0)2 4173 5364
fax: (33) (0)2 4173 5216
Two laser beams at a fundamental and its harmonic frequency can interfere in materials. It is not usual but it occurs provided there is
some coherence properties between excitations at both frequencies.
This is the case in polymers containing noncentrosymmetric molecules. (The effect was dicovered in 1986 by Österberg and
Margulis in optical fibers).
The interference between two beams at different frequencies is particular : we show that it induces an interference grating which is
not associated to any index modulation. The interference grating is a phase-matched one (namely the one which is needed to to
provide the wave vector mismatch in order to recover constructive interference of the second harmonic amplitudes generated in
different régions of the medium). After a review of the many possibilities and features of the effect, we illustrate an example in
which we use the all-optical poling process in order to print and recover an holographic image.