Encoding of macroscopic second-order non-linearity via all-optical polar alignment in substituted norbornene polymer thin films

Efficient all-optical poling of substituted norbornene azo-molecules-doped polymer thin films is presented. The growth and decay of photoinduced second-order susceptibility χ(2) has been studied. The possibility of encoding χ(2) at low seeding intensities (about 10 MW/cm2 for fundamental and 100 W/cm2 for second harmonic) is demonstrated. The value of encoded χ(2) in mono-norbornene-doped polymethylmethacrylate (PMMA) and poly-norbornene polymer have been found to be with the same order of magnitude despite the latter revealed considerably higher first hyperpolarizability. This is due to the rigidity of the poly-norbornene polymer backbone and the strong orientational correlation between pendant chromophores that reduce reorientation of molecules.