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a b s t r a c tA series of single Q2 co-crystals of non-centrosymmetric complexes of different mono-and diaminopyridines, namely 4-aminopyridine, 3,4-diaminopyridine, 2-amino-6-methylpyridine, 2,6-diaminopyridine, 2-aminopyridine, with 4-nitrophenol were grown by slow evaporation technique from solution at constant temperature. Optical transparency in the region of 300-1100 nm was found to be suitable for nonlinear optical applications with cut off wavelengths at 420-474 nm for these co-crystals. Single crystal X-ray analysis confirms the non-centrosymmetric packing. Thermogravimetric and differential thermal analysis shows good thermal stability of the studied compounds with melting point at range 99-172°C for different co-crystals. The second harmonic generation efficiency has been measured on single crystals by comparative SHG technique relative to KTP crystal. The nonlinear optical coefficient of the compounds was found to be up to 39 pm/V.

Two-dimensional photonic crystal structures (PCS) were fabricated using a one-step recording process, multi-beam interference in smart polymer nanocomposites incorporating SiO2 and Au nanoparticles sensitized to 532 nm laser radiation. It was shown, that PCS with different geometry can be recorded in thick nanocomposite layers. The typical two dimensional (2D) PCS have square structure with 2-8 µm period, being in good agreement with theoretical structures obtained by mathematical modeling of the recorded PCS. The peculiarities of the photo-polymerization of nanocomposites with plasmonic Au nanoparticles were analyzed on the basis of Surface Plasmon Resonance Imaging (SPRi) and Raman spectroscopy investigations and used for the interpretation of the recording process and periodic structure formation. Abstract Two-dimensional photonic crystal structures (PCS) were fabricated using a one-step recording process, multi-beam interference in smart polymer nanocomposites incorporating SiO 2 and Au nanoparticles sensitized to 532 nm laser radiation. It was shown, that PCS with different geometry can be recorded in thick nanocomposite layers. The typical two dimensional (2D) PCS have square structure with 2-8 µm period, being in good agreement with theoretical structures obtained by mathematical modeling of the recorded PCS. The peculiarities of the photopolymerization of nanocomposites with plasmonic Au nanoparticles were analyzed on the basis of Surface Plasmon Resonance Imaging (SPRi) and Raman spectroscopy investigations and used for the interpretation of the recording process and periodic structure formation.

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Cuboid-shaped organic microcavities containing a pyrromethene laser dye and supported upon a photonic crystal have been investigated as an approach to reducing the lasing threshold of the cavities. Multiphoton lithography facilitated fabrication of the cuboid cavities directly on the substrate or on the decoupling structure, while similar structures were fabricated on the substrate by UV lithography for comparison. Significant reduction of the lasing threshold by a factor of ~30 has been observed for cavities supported by the photonic crystal relative to those fabricated on the substrate. The lasing mode spectra of the cuboid microresonators provide strong evidence showing that the lasing modes are localized in the horizontal plane, with the shape of an inscribed diamond.