Organic materials possessing quadratic non linear optical (NLO) properties are now part of the optical material panel available for applications. Up to now, the patterning of their optical properties for device fabrication is commonly achieved by the lithographic techniques derived from the microelectronic domain. We propose here an alternative method that allows a direct patterning of the NLO properties. The objective is to manufacture quasi phase matched devices for optical frequency conversion in guided mode and in the regime of free propagation.
Photopolymers are already well known as holographic materials. The modulation of the refractive index is patterned by the distribution of the cross-linking rate which depends on the illumination conditions. More recently, it has been demonstrated that the quadratic non linear optical (NLO) properties can be patterned in photopolymerized materials doped with push-pull chromophores. In that case, one takes advantage of the huge increase of the viscosity during the polymerization process to freeze the chromophores orientation. By using adapted sequences of applied electric field to orientate the polar NLO molecules combined with appropriate illumination conditions, it is then possible to create periodic poled structures in such doped photopolymers. The technique is therefore especially adapted for the realization of quasi phase matching structures in organic materials.