Oriented Thin Films for Nonlinear Optics

F. Kajzar, A. Lorin Commissariat à l'Energie Atomique, Direction des Technologies Avancées LETI, DEIN/SPE/GCO, CE Saclay, 91191 Gif Sur Yvette Cedex, France J. Le Moigne Instutit de Physique et de Science des Materiaux, 23, rue du Loess, 67037 Strasbourg, France and J. Szpunar Department of Mining and Electrical Engineering, Mc Gill University, 3450 University Street, Montréal PQ, Canada H3A 2A7

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Nonlinear optical dichroism technique is shown to be an useful tool for the 1D conjugated polymer chain orientation study. When done as a func­tion of rotation angle it gives the order parameters. These parameters can be also obtained by coupling this technique with linear dichroism method. The technique is illustrated by third harmonic generation on epitaxied poly­diacetylene thin films either on single-crystalline or on preoriented ultrathin films by rubbing. Whereas an almost perfect orientation is obtained in the case of epitaxy of p-DCH, poly [1,6-bis(N-carbazolyl)-2,4-hexadiyne], on KAP, potassium acid phthalate, single crystal, this is smaller for epitaxy on preoriented substrate. The results are correlated with thin film texture mea­surements with X-rays. A good overall agreement is seen except that X-ray data show better order than nonlinear optical dichroism. A possible origin of this difference is shortly discussed.

DOI: 10.12693/APhysPolA.87.713 PACS numbers: 42.65.-k, 78.20.-e, 83.80.Es