Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Final Activity Report Summary - NANONLO (Nanostructured Materials with Nonlinear Optical Properties)

The NANONLO project concerned the development of new competences at the host for the synthesis and processing by thermal poling of novel materials and the characterisation of their second-order optical properties induced by synthesis and post-synthesis treatments. To this aim, the host institute recruited three experienced researchers in thermal poling, non-linear optical (NLO) properties, glassy and hybrid materials. In addition, researchers of the host institute were trained at two highly-experienced partner laboratories in Bordeaux, France, to ensure a durable transfer of knowledge in the sought new competences.

The work plan of the project involved research and development activities for the fabrication at the host of experimental set-ups for thermal poling and second-harmonic generation (SHG) measurements, and for the synthesis and investigation of novel materials with potential NLO properties. In this context, inorganic glasses, glass-ceramics and soft hybrid materials were considered due to their potential in the field of photonics. This research was driven by the current needs of optical communication technologies for versatile and inexpensive materials with NLO properties, which could replace eventually the difficult to synthesise and expensive ferroelectric crystalline materials used nowadays. Inorganic glasses and glass-ceramic materials were developed in bulk and thin film forms in several systems containing highly polarisable ions, e.g. Nb5+, Ge4+, Pb2+, and were thermally poled at different conditions to induce strong SHG activity.

Combined structural studies (micro-Raman, micro-infrared) with micro-SHG mapping and macro-SHG simulations allowed to determine (i) the effects of poling conditions on the thickness of the NLO layer, its SHG efficiency and the local network structure; (ii) the charge compensation mechanisms in the NLO layer as triggered by the movement of mobile ions under the poling voltage; (iii) nanocrystal orientation in bulk glass-ceramic materials; (iv) poling-induced formation of ferroelectric nanodomains in thin amorphous films; and (vi) useful structure-NLO property correlations.

Work on functional soft materials involved synthesis and studies in several hybrid systems based mainly on methacrylate-type polymers containing NLO chromophores, such as PMAA-xDR1, PHPMA-xDR1, PMEO-xDR1 where x is the wt% content of chromophore DR1 and the polymer matrices differ in size and polarity of side chains. Studies focused on structure (NMR, infrared, Raman, hyper-Raman, optical spectroscopy), thermal properties and stability (DSC, DTA), hyper-polarisability (hyper-Rayleigh), and SHG activity as a function of materials chemistry and corona-poling conditions.

Key results concern (i) enhancement of SHG with poling temperature in PHPMA-xDR1 films by effective alignment of chromophores; (ii) enhancement of NLO activity and stability in PMAA-xDR1 films by anhydride formation and cross-linking of the polymer matrix, and (iii) generation of NLO activity by self-alignment in spin-coated PMEO-xDR1 thin films. Results of the project were presented at numerous conferences, at three workshops and several lectures at the host and partner institutes, and were published as peer reviewed articles in many journals.

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